Ok, the problem came back today. I went ahead and deleted all of the files out of the cache folder, but not the folder itself. When re-entering the game the cache was built again, but the problem remains.
Just prior to this, I was locked up in the hangar. By 'locked up' I mean that the clipboard would not allow any function other then the selection of a vehicle/plane. Couldn't get to tower, quit etc. Had to Alt-F4 out.
Just to recap, what I see is the game will start, and offline play is fine. The arenas will load, and I can see the number of players etc. When entering an online arena, part of the map/tower loads and then I'm booted to the desktop.
Since this happened without a patch or update this time it may not be a bug so much as a TS issue, so feel free to move the thread. I can always do another reinstall to fix the issue for the weekend if I have to.