[Cryptic1]

I have 3 XP Pro computers networked via a Workgroup. All 3 computers show up in the workgroup on all 3 computers. I have the C drive shared on all 3 computers. One computer can access everything. The other 2 computers can access each other, but both can't connect to the first one. In other words...
A can access B & C.
B & C can access each other, but not A (but it does show in the workgroup for all 3).
When I try to access A (from B or C), I get an Access Denied prompt that says I may not have permission to access. I have all 3 connections set up exactly the same (in Local Area Connection), and have C shared with both, "Share this folder on the network", and "Allow network users to change my files" checked.
The only protocol I'm using is TCP/IP. I've tried with windows firewall on and off. I'm out of ideas. Any suggestions?
Thanks in advance.

CJ