XP Mapped Drives Initial connection Slow to NAS.. WHY?

Hello.. So I have to apologize as dont know all the details but I will provide you with everything I have. So we have a mixed environment of Win 7 machines and XP Pro machines all on a Domain. We are trying to migrate our shared folders to a NAS from Novell server. Since we moved some files to the NAS our XP machines experience a slow response on the initial double click of the network drive but after a lag of anywhere between 15-25 seconds performance is fine. However, if the end user does not use that drive for a certain amount of time (not talking minutes, could be 2 hours or such) when they double click the drive, it lags again 15-25 seconds. Windows 7 works just fine..

When I map to the hostname\share lag is 15-25 seconds (Remember Win 7 is fine, this is just XP)
When I map to the ip 10.12.x.x\share the lag is normal 2-5 seconds

All machines are using the same DHCP, same DNS.

So my questions are:
1) Is there a session timeout on the NAS that kicks users off that havent had activity to free up the connections? I have read about "NoSMBDisconnect". Is that something that could be the issue with the disconnect?
2) Why the lag of 15-25 secs on the XP machines and not Win 7?

PLEASE HELP!