This is exactly the problem I had when Office Starter 2010 interfered with RB's network ports.
(discussed in several other post on the forum)
The problem I had with finding out what software caused it, was that it locked the ports at startup, and then didn't fully released them, so when I checked it looked like all ports where ok.
Have you tried to reboot the computer in "safe mode WITH network" and then tried to use Pro link?
If that works, you have some sort of software interfering with the ports in normal mode.