My journey through x64 land is getting more frustrating by the minute. When I tried to connect to my dedicated server box via RDP, I got the following error message:
The specified remote computer could not be found. Verify that you have typed the correct computer name or IP address, and then try connecting again.
"That can't be!" was my first reaction. Especially because I use the very same host for email, and that was working from the start. So I fired up my trusty X31 laptop and tried there - working just fine!
Next, I compared the TCP/IP settings - both identical, because I use DHCP in my network to dole out IP configurations. Back to the basics. Ping. Working fine on my laptop, not working on my x64 box. Scratch, scratch. Wait a second! Because I am paranoid, I don't configure the default gateway for my machines, so that when I turn off the ISA client, I have no Internet connectivity whatsoever (nice for testing).
Turns out that the email program makes proper (high-level) use of the network stack, however, ping and mstsc go lower, and - nasty surprise - the ISA client doesn't work properly on x64 (thread here). Now that is the second time that my "no default gateway policy" rears its ugly head (instance #1).