EDIT

New info: Navigating to localhost:1434 in Chrome gives me an "ERR_EMPTY_RESPONSE", while other ports give me an "Oops! This link appears to be broken". So it seems to binding ok there?

So here's my setup so far:

• I've configured Windows Firewall to allow TCP on 1433 and UDP on 1434.
• I've set up SQL Server to use any IP on Port 1433 (using the SQL Server Configuration Manager).
• My hosts file contains the default entries ("127.0.0.1 localhost" and "::1 localhost").
• I sometimes have a debug session of Visual Web Developer running a webserver, but it's on a specific port (localhost:5XXXX).

What I've tried:

• I CAN ping localhost in a cmd prompt.
• I CAN connect to the database through SSMS if I specify 127.0.0.1 or ::1 as the server name.
• I CAN'T connect to the database through SSMS (or ADO.NET) if I specify localhost as the server name. I've tried both Windows and SQL Authentication The error I get is the standard

Can't connect to localhost. Additional Information --> Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. (Microsoft Sql Server)

Other considerations:

• Stopping the Visual Web Developer web server from the taskbar doesn't affect the sql problem.
• The SQL error log says that it's listening on some piped name url at start up (I don't see how this would affect localhost but not 127.0.0.1 though).

I could probably just use 127.0.0.1 everywhere, but it scares me that localhost isn't working and I'd like to figure out why.

I'm not much of a networking or sql server guy so I'm stuck. If you want me to try anything to help diagnose just put it in a comment and I'll give it a go.

Netstat results:

Setting SDK environment relative to C:\Program Files\Microsoft SDKs\Windows\v6.1

Targeting Windows Server 2008 x86 DEBUG

C:\Program Files\Microsoft SDKs\Windows\v6.1>netstat -ano | findstr 1434
  UDP    0.0.0.0:1434           *:*                                    6868
  UDP    [::]:1434              *:*                                    6868

C:\Program Files\Microsoft SDKs\Windows\v6.1>netstat -ano | findstr 1433
  TCP    0.0.0.0:1433           0.0.0.0:0              LISTENING       2268
  TCP    127.0.0.1:1433         127.0.0.1:50758        ESTABLISHED     2268
  TCP    127.0.0.1:50758        127.0.0.1:1433         ESTABLISHED     5008
  TCP    [::]:1433              [::]:0                 LISTENING       2268
  TCP    [::1]:1433             [::1]:51202            ESTABLISHED     2268
  TCP    [::1]:1433             [::1]:51616            ESTABLISHED     2268
  TCP    [::1]:51202            [::1]:1433             ESTABLISHED     5008
  TCP    [::1]:51616            [::1]:1433             ESTABLISHED     5008

C:\Program Files\Microsoft SDKs\Windows\v6.1>

SQL Server Log File:

In case it helps

2010-01-30 12:58:59.01 Server      Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (Intel X86) 
    Mar 29 2009 10:27:29 
    Copyright (c) 1988-2008 Microsoft Corporation
    Express Edition on Windows NT 6.0  (Build 6002: Service Pack 2)

2010-01-30 12:58:59.01 Server      (c) 2005 Microsoft Corporation.
2010-01-30 12:58:59.01 Server      All rights reserved.
2010-01-30 12:58:59.01 Server      Server process ID is 2268.
2010-01-30 12:58:59.01 Server      System Manufacturer: 'Dell Inc.', System Model: 'Inspiron 1545'.
2010-01-30 12:58:59.01 Server      Authentication mode is MIXED.
2010-01-30 12:58:59.02 Server      Logging SQL Server messages in file 'c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\Log\ERRORLOG'.
2010-01-30 12:58:59.02 Server      This instance of SQL Server last reported using a process ID of 7396 at 1/30/2010 12:57:38 PM (local) 1/30/2010 5:57:38 PM (UTC). This is an informational message only; no user action is required.
2010-01-30 12:58:59.02 Server      Registry startup parameters: 
     -d c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\master.mdf
     -e c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\Log\ERRORLOG
     -l c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\mastlog.ldf
2010-01-30 12:58:59.02 Server      SQL Server is starting at normal priority base (=7). This is an informational message only. No user action is required.
2010-01-30 12:58:59.02 Server      Detected 2 CPUs. This is an informational message; no user action is required.
2010-01-30 12:58:59.08 Server      Using dynamic lock allocation.  Initial allocation of 2500 Lock blocks and 5000 Lock Owner blocks per node.  This is an informational message only.  No user action is required.
2010-01-30 12:58:59.17 Server      Node configuration: node 0: CPU mask: 0x00000003 Active CPU mask: 0x00000003. This message provides a description of the NUMA configuration for this computer. This is an informational message only. No user action is required.
2010-01-30 12:58:59.30 spid7s      Starting up database 'master'.
2010-01-30 12:58:59.41 spid7s      Recovery is writing a checkpoint in database 'master' (1). This is an informational message only. No user action is required.
2010-01-30 12:58:59.67 spid7s      FILESTREAM: effective level = 0, configured level = 0, file system access share name = 'SQLEXPRESS'.
2010-01-30 12:58:59.92 spid7s      SQL Trace ID 1 was started by login "sa".
2010-01-30 12:58:59.94 spid7s      Starting up database 'mssqlsystemresource'.
2010-01-30 12:58:59.95 spid7s      The resource database build version is 10.00.2531. This is an informational message only. No user action is required.
2010-01-30 12:59:00.82 spid7s      Server name is 'DELL\SQLEXPRESS'. This is an informational message only. No user action is required.
2010-01-30 12:59:00.83 Server      A self-generated certificate was successfully loaded for encryption.
2010-01-30 12:59:00.84 Server      Server is listening on [ 'any'  1433].
2010-01-30 12:59:00.84 Server      Server is listening on [ 'any'  1433].
2010-01-30 12:59:00.84 spid10s     Starting up database 'model'.
2010-01-30 12:59:00.85 Server      Server local connection provider is ready to accept connection on [ \\.\pipe\SQLLocal\SQLEXPRESS ].
2010-01-30 12:59:00.86 Server      Server local connection provider is ready to accept connection on [ \\.\pipe\MSSQL$SQLEXPRESS\sql\query ].
2010-01-30 12:59:00.86 Server      Dedicated administrator connection support was not started because it is disabled on this edition of SQL Server. If you want to use a dedicated administrator connection, restart SQL Server using the trace flag 7806. This is an informational message only. No user action is required.
2010-01-30 12:59:00.87 Server      The SQL Server Network Interface library could not register the Service Principal Name (SPN) for the SQL Server service. Error: 0x54b, state: 3. Failure to register an SPN may cause integrated authentication to fall back to NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies.
2010-01-30 12:59:00.87 spid7s      Informational: No full-text supported languages found.
2010-01-30 12:59:00.87 Server      SQL Server is now ready for client connections. This is an informational message; no user action is required.
2010-01-30 12:59:00.91 spid7s      Starting up database 'msdb'.
2010-01-30 12:59:01.21 spid10s     Clearing tempdb database.
2010-01-30 12:59:02.78 spid10s     Starting up database 'tempdb'.
2010-01-30 12:59:03.30 spid13s     The Service Broker protocol transport is disabled or not configured.
2010-01-30 12:59:03.30 spid13s     The Database Mirroring protocol transport is disabled or not configured.
2010-01-30 12:59:03.31 spid7s      Recovery is complete. This is an informational message only. No user action is required.
2010-01-30 12:59:03.31 spid13s     Service Broker manager has started.