smbfs crashes after inactivity

[Robert Hawkey <roberth@hb-studios.com>]

I know this probably isn't the best list for this question but...

We've got several machines set up in our office running Debian, RedHat
and Slackware Linux that all mount a share on our Windows 2000 server. 
If any of the machines don't use the share for longer than a half hour
or so Samba crashes and you can no longer access the share.  If you do
an ls on the share it will say "ls: Input/Output error".

When the crash occurs you cannot umount the mounted folder, all that
happens when you type "umount /sambashare" is umount runs, and quits
with no messages, but when you try to remount the share it tells you
that the share is already mounted.  The only way to get the share back
is to reboot the machine.

Does anyone know why this is happening?

Here's the command we use to mount the share:

mount -t smbfs -o
username=<user>,password=<password>,rw,fmask=0777,dmask=0777
//192.168.0.2/<SHARE NAME> <folder on our machines>

Thanks,

Robert Hawkey