How come one user in the local Administrators Group has no problem hitting http://localhost:8080/services/v1.0/Registration.asmx while other users in the local Administrators Group get 403 (access denied) errors (with nothing in the Event log)?
Have you checked the permissions of all three areas. You need permisssion on server, reporting service and sharepoint for this.
I would strongly recommend you download Team Foundation Server Administrator tool to do this as otherwise it can be a right pain.
dove, I’m not sure about how the Team Foundation Server Administrator tool would help here. I installed it on the TF server and got an empty interface that looks like it is expecting pre-exiting Team projects.
rasx, yea, the interface isn't the best on that tool. It basically allows an easy way to set up permissions to the Team Foundation Server, Reporting Services, and Sharepoint.
Most of the security problems I've come across always resolve down to one of those three permissions messed up on a particular user. I'm pretty sure that's what you're experiencing. Without the Team Foundation Administrator Tool that dove mentioned, you can still just add permissions to each of those areas manually.
It sucks that TFS doesn't come with an easy way to manage all permissions everywhere, but there you have it.