slow unc resolution on a win 2008 share

Are you using Symantec Enterprise Security 11? There is an issue with 2008 and server shares on older updated versions; not sure if this is your issue but something to look into if you are using symantec (I didn't see any statement about A/V software).

http://www.symantec.com/connect/forums/mr3-locks-server-2008-file-shares

I noticed this problem on my first 2008 file server after about 20/30 users started using it. It got progressively slower then finally just gave up sharing files but everything else (RDP, etc.) worked fine. After ripping hair out I found it to be the A/V problem stated above.

Have you a Broadcom NIC in the server and is the TCP offload engine enabled? This is a configuration known to cause trouble, so it's certainly worth checking out and disabling the offload engine if required.