Network shares not accessible in Windows 2008

I have recently installed Windows server 2008. After that upgraded it as a Domain controller. (more information will come in future about this) Since after that our internal users have
experienced network /connection problems to the server.
At least once a day I must reboot the server so that users can access the shared folders in the server. Since I host a database in this machine this problem has become a real headache and a panic to me.

Users with offline files get notice that they are no longer connected to the server. They can't sync etc.
When this happens you can still ping the server. Remote desktop to the server works 100% and the server seems to be working without any error.Tested the cabling and all the links passed the tests.

So finally found out the problem relates to Symantec EndPoint protection anti virus software. I've been using ver 11 MR2. Further digging into this matter came up with the below mention article released by Symantec

http://service1.symantec.com/support/ent-security.nsf/docid/2008061812370848?Open&seg=ent

Apart from that Microsoft has acknowledged this problem can occur if you're having outdated NIC driver.

After removing the AV software users back to business. I guess I'll have to test out the latest version of the Symantec (MR3) and then see if that solved the problem. Will update you all once I get my hands into SEP MR3 version.