On my network, my edge-router, a windows 2003 r2 server router with all the latest updates, will drop packets, but only under specific circumstances. I have troubleshot and isolated it down to the most simple configuration i can. There is NO NAT involved. Only fully-public IP addresses. No Firewalls are running either, all ahve been disabled. no packet filters on any interfaces anywhere either.

I have a single Windows XP virtual machine and my edge-router(the windows 2003 r2 server, and also a virtual machine) running on a windows 2008 x64 r2 system (running virtual server 2005 as i dont have Intel-VT compatible chip yet).

The edge router can access any external http site just fine, no issues. However the windows XP machine is only able to access certain sites. These work: www.google.com www.txstate.edu www.workintexas.com www.thedailywtf.com . These Dont: www.yahoo.com www.utexas.edu en.wikipedia.org slashdot.org www.bing.com.

I have removed all possibility of DNS issues by connecting with net-cat from the XP box and sending GET /\r\nHost: \r\n\r\n and that connection replicates the issue as well.

The network setup: My statically assigned IP block: x.x.x.168/29

     DSL Modem  -----PPPoE Connection---- x.x.x.169[EdgeRouter]
     [EdgeRouter]x.x.x.170 -----Virtual Ethernet----- x.x.x.174 [Test2]

Test2's Default gateway is x.x.x.170 and test2 can ping any and every valid, accessible, public IP address with no packet loss what-so-ever. If i connect directly over PPPoE from test2 (the XP box) everything works just fine...

Im at my wits end, i have NO IDEA whats causing this.