Win/XP Pro SP2 creates You might not have permission to use this network resource message

Navigating Entire Network -> MS Windows Network -> workgroup name
creates
Symptom:

Workgroup is not accessible.
You might not have permission to use this network resource.
Contact the administrator of this server to find out if you have access permissions.

YET: in My Network Places you can add any system on your lan and access it just fine!

What gives?

Network places is working because ports 139,445 are open in the firewall.
Workgroup access is failing as ICS is not active.

Solution:

Enable Windows Firewall/Internet Connection Sharing(ICS)

Both Network places and Workgroup name access will now work.

(spend serveral hours working this )

Thank-you jobeard, as stated in another post (can't remember where now)
When I installed passwords on accounts, it seemed to have worked too

But actually all this may be to do with Windows Firewall/Internet Connection Sharing(ICS) ONLY
ie creating a password, probably automatically turned on the service