I am using XP Home not XP Pro, but assume that the Wizard works the same way. When you used the Wizard did you ensure that the Computer Description and Computer Name for each PC were different, if this is NOT the case then that will be where the problem lies. The only common name would be the Workgroup Name.
If you are using Norton Internet Security, then you will also have to run the Norton Network Wizard so that the IP and Mask addresses for each PC are in the Trusted Zone.
If your problem persists I would suggest you post in the Network forum rather than here, as that Forum is specific to Network problems. I have used it a few times and the responses are excellent.