I have a VPS running Windows Web Server 2008 R2. I'm able to connect using Remote Desktop from my home PC (Windows 7), personal laptop (Windows 7), and work laptop (Windows XP).

However, I cannot connect from my work PC (Windows 7). I receive the error "The logon attempt failed" in the RDP client, and the server event log shows "An account failed to log on" with this explanation:

Subject:
    Security ID:        NULL SID
    Account Name:       -
    Account Domain:     -
    Logon ID:       0x0

Logon Type:         3

Account For Which Logon Failed:
    Security ID:        NULL SID
    Account Name:       username
    Account Domain:     hostname

Failure Information:
    Failure Reason:     Unknown user name or bad password.
    Status:         0xc000006d
    Sub Status:     0xc0000064

Process Information:
    Caller Process ID:  0x0
    Caller Process Name:    -

Network Information:
    Workstation Name:   JESSE-PC
    Source Network Address: -
    Source Port:        -

Detailed Authentication Information:
    Logon Process:      NtLmSsp 
    Authentication Package: NTLM
    Transited Services: -
    Package Name (NTLM only):   -
    Key Length:     0

I can connect from the offending work PC if I start up Windows XP Mode and use the RDP client inside that.

The server is part of a domain but my account is local, so I'm logging in using a username of the form hostname\username. None of the clients are part of a domain. The server uses a self-signed certificate, and connecting from home I get a warning about that, but connecting from work I just get the logon error.