I’ve seen something weird for quite some time on my WinXP clients. When I attempt to map a shared drive, WinXP first tries to access port 80 before hitting the expected port 445. Turns out that WinXP by default checks port 80 first before port 445 for its WebDAV Redirector. If the server is behind a firewall and port 80 is blocked, there is a lengthy delay before the share pops up.
I believe it’s possible to disable the WebDAV Redirector, but I haven’t messed with it yet.