We're in a small satellite office connected to our HQ over a VPN connection. The connection itself is not bad, ping times are around 100 ms, remote access, telnet and FTP speeds are fine.
However, connecting to HQ's Windows servers from our Windows clients is absolutely horrible. Generally, I do this via 'My Computer', using \server, possibly followed by path. Displaying a 10-item directory can require upwards of 2 minutes of hourglass watching.
If I 'net use' the server, directory listings are much faster, so it seems to be a 'My Computer' problem.
I'm using Windows XP 64-bit, but all 10 machines at this site (Vista, Win7, etc) all exhibit this problem to one extent or another.
Unfortunately, I cannot at this time tell you much about the network topology at our HQ site, but I can ask if anyone has any specific questions.