Lost Credentials?

[Matt K]

Environment: 1 WIN2K server, 2 XP Pro workstations.
Workstation "A" has a HP 6P laser attached to the LPT
port.
When working on workstation "A", I can regularly access
drives mapped to the server as expected. However,
accessing mapped drives and printing to a printer
attached to workstation "B" works until activity is idle
for, say, overnight. The next time I attempt to access or
print to workstation "B", it seems as though my
credentials are lost and the only way to re-attach and
print to workstion "B" is to log off and log back on.
Ideas? (Side note: Logging back on does take a bit long)
Thanks in advance for any input.