Long delay accessing VIsta file shares

For some reason, when I try to access a Vista file share from a
Windows XP virutal machine, there is a long delay the first time I
access it before it gives me the directory listing. This delay
partially locks up the XP computer.
Also, if I try to access a Vista file share from Windows 98SE, either
the real computer or a virtual one, it causes Win98 to lock up
completely.
Vista has no problem accessing either OS's file shares, but the
Win98SE print shares don't work after rebooting. That's a separate
issue I made a separate post in the printing newsgroup.
The XP virtual machine has no networking problems with the real
Win98SE computer and win98Se has no problems with the virutal machine.
It's only accessing Vista shares that I have problems. The delay is
extremely annoying in XP, but is a critical failure trying to do
anything in win98se, forcing me to make that old computer the file
server. Which is also making me inclined to do the actual work on the
old, obsolete machine that works whenever possible.