Timeout and disconnect MACSRV

Hello,
Using a Windows 2003 Enterprise Server in a
predominantly Macintosh prepress network for a printing
company. Wide range of machines OS 7.5 to OS X 10.2.8. and
a few Wintel boxes. File Services for Mac is running.
On the Win 2000 PC and the newer Mac OS machines we keep
getting disconnected from the server. The events system
log reports the following when the Macs get kicked off -
_______________________
Source: MACSRV
Event ID: 12061

Session from user "g4-2" was timed out and disconnected by
the server. The IP address of the Macintosh workstation is
in the data.
_______________________

The events security log reports the following when the
PC gets kicked off but the PC "automatically" re-logs
itself in so isn't terrible unless it does it in the
middle of file operations -
_______________________
Source: Security
Categpry: Logon/Logoff
Event ID: 538

User Logoff:
User Name: p41800
Domain: 2003SERVER
Logon ID: (0x0,0x4D1E19)
Logon Type: 3
_______________________

The security event log for the Macs reports this -
_______________________
Source: Security
Categpry: Logon/Logoff
Event ID: 538

User Logoff:
User Name: g4-2
Domain: 2003SERVER
Logon ID: (0x0,0x4F1F6D)
Logon Type: 3
_______________________

The disconnect occurs when the machines are idle and
more often during file operations such as writing a
postscript file to disk from Quark Express.
The Macs require us to "remount" and "reauthenticate"
manually. It is particularly troublesome during file
operations and appears to happen more frequently when
working with large files. We commonly deal with 50 MB
files and larger. A job giving us trouble today is nearly
2 GB in size.

Thanks,
Chris Yates