Trading works for me, and I use MM and AGS. So....
1. Have you updated your addons? They have been getting updated every day since CWC dropped
2. Have you tried trade without any addons? If it works, add half of them back, see if it pukes, then try the other half. Work through them until you find the problem child and do something about that mod.
3. Frequently I can get the UI errors to not show up by using a Right Click and choose something from the Context Menu.
Enjoy the game, life is what you really want to be worried about.
PakKat "Everything was going well, until I died"
Gary Gravestink "I am glad you died, I needed the help"
I'm afraid I DO need to update my add ons. It alerted me when I logged in tonight. I've only got a couple so won't take long. That's probably it and wasn't even thinking that could be the issue.
I'll report back later tonight or tomorrow, real life calls.