Windows XP networking issue

I have 2 pcs running WinXP going through the same hub on the same workgroup and i have made identical accounts on each. After the initial install i oculd view the shared folders, but after i ran sp1, and critical updates on both pcs, I now get a access error, you may not have permissions, contact your network administator.

I can still see both pcs under the workgroup. Anyone have any ideas as to what this is ? .. I am assuming it is a security policy issue.

Thanks.