One instance jittering

I am trying to dual-box and the main is stuck on 5-10 fps and very jittery, It stays this way if switched to the background and the new main runs perfectly fine at 60 fps, I can load more WoWs and they work fine. I have tried restarting everything and creating an entirely new character set, it was working fine last night.

The setting that allows you to choose the FPS of back and foreground windows may have gotten swapped inadvertently. Be sure to double check those, just my first blind guess at the issue.

Did you export since it was working?