Mapped Home Drives disappear

Hello all,

I would appreciate any help that anyone can give on this
subject.

I set up for my customer about 8 months ago a new network
system including (2) Win2003 servers w/all patches and
approx 40 clients running XP Pro. They have a Cisco 48-
port switch.

Everything was great until about 6 weeks ago when users
were "randomly" losing their home drive connection. The
mapped drive would just disappear from their "My Computer"
and they would be forced to log in again to reconnect.
Other shared network resources displayed the usual red X
after a period of inactivity but would reconnect.

According to the customer (I haven't been out there
lately), this problem has been happening more often and to
more clients.

I'm aware of Win2003srv temporarily "disconnecting" drives
to save resources, but this is not that.

Thank you in advance for any help you can provide.

-Jim