I have a user who uses a Windows 7 computer and has a drive mapped to a drive on a windows server 2003 machine. However, she is having trouble copying files over 1 MB in size from the Windows 7 machine to the drive. The little copying dialog comes up, says "calculating," and then hangs. She's let it run overnight and it was still going the next morning. The only way to get rid of the dialoge is to restart the machine.
Interestingly enough, she can copy files from the mapped drive back to her own computer with no trouble at all. Further more, none of our other Windows 7 users are having this issue.
I've made sure that network discovery was turned on. I've also tried to reproduce the problem using my account and succeeded. Booting up into Safe Mode with Networking seems like it allows us to copy the files, although we didn't try anything larger than 46 MB.