Vista networking problem

I have a problem with accessing files on a Windows server 2003 Domain using a laptop running Vista Ultimate on a workgroup.

I can access all shares on the domain except those located directly on the Windows 2003 servers. All of the shares on XP pro sp2 computers are accessible with no problems. Another laptop also running Vista home premium that is on the workgroup has no problems getting access to files on 2003 server. It requires domain credentials but that is fine.

I have tried using same login on laptop as user has on domain but it didn’t seem to help. I’ve also tried browsing with IP and share name in windows explorer still can’t get access. Any info to point me in the right direction would be greatly appreciated.