LinuxQuestions.org - Question about Samba timeout

I asked this in the general forum and didn't get an answer.. maybe it's more of a newbie question..

here's the setup i have.. I have a RHEL4 server running samba-3.0.10. I have several WinXP laptops that map network drives to the server so they can run a Windows backup program that backs up to the network share.
I've tried two different backup utilities, one being a program my company created and the other being the build in Windows ntbackup utility. Both programs will backup to the network share with no problems when the backup is run manually, but if the backup is scheduled, sometimes it will fail saying the 'specified media cannot be found'. We leave the drives mapped all the time and have them set to reconnect on boot.
But i'm wondering if Samba has some kind of 'timeout' period? I've read that in Windows, there's a registry option that stops the default 15 minute timeout on the server side (where you show the drive in My Computer, but it's got the red X or whatever it is, and you just dbl click it and it reconnects instantly).. Is there something like that in Samba?

I've tried adding "change notify timeout = 0" to my smb.conf, but that didn't seem to fix the problem..
anyone have any other ideas?
It's only affecting people who have their network share mapped for a while (several days).