I had an issue with virtual machines not talking to each other.  I took a production SBS 2003 server and a production XP client workstation to that same domain and used Disk2VHD to create virtuals out of them so I could test a migration to SBS 2008 on a Hyper-V server. 

From research, it seems like the problem has to do with Symantec Corporate Antivirus.

I removed Symantec AV from the server and the workstation and the SRV error messages in the Event logs went away and the machines started communicating.

On the server or local machine you might get this following message in the event viewer.
"The server's configuration parameter "irpstacksize" is too small for the server to use a local device. Please increase the value of this parameter".

One fix that did not seem to fix in my case was:

You'll have to add then following to the local pc's registry. 
- Go to HKLM\SYSTEM\CurrentControlSet\Services\lanmanserver\parameter
- There edit the IRPStackSize value to 18 Decimal or 12 Hex.
- If the value is missing insert a new DWORD Value and name is IRPStackSize as it is spelled here with upper and lower case.
- After this you restart the computer and login. You should now be able to access shares accross the network