I too have been having these problems, tried mapping the printers with GPO, Con2Print, and VBS scripts, the problem does not seem to matter what mapping method is used. We used Con2Print with our XP clients and the same print server for years with no issues, now that we've taken our computer labs to Win7 we have this problem. If we use GPO, the login time can vary anywhere from 30 seconds to 5 minutes, con2print the login is instant but the mapping process can again take 30 seconds to 5 minutes, though more often than not it fails on the mapping almost instantly and once it fails that workstation cannot connect to any printers off the printer server until it is rebooted (or the spooler server is bumped).
It almost seems like some kind of DNS or network problem. Our print server is 2k3 32bit, but I tried setting up a 2k8 64bit over the summer and the issue was even more pronounced. Just for experimentation's purpose, I tried running a 2k8 32 bit, and a 2k3 64 bit server as well, again the issue persisted, more pronounced from 2k8 servers.
The only variable that changed was taking our client workstations to Win 7 32bit from XP 32bit. I've dug all over the internet and found people with the same issues, but no real resolution.
Quite frustrating.
