If iTunes sees your device and TU does not then this indicates the problem is with your PC. TU uses the same mechanism as iTunes to connect to your device so it is very unusual for one to see the device and the other to not. Are you running TU as an Administrator account?
Also, don't let this keep you from jailbreaking. Once you jailbreak and start Cydia, your blobs will be automatically saved for 5.1.1 on Cydia's servers. After that, you can worry about getting TU working.
Yes, running as administrator. Tried again just t make sure. Same issue - iPad 3 doesn't show up in device list on left.
Thanks for the advice to go ahead and JB