Here's a few ideas (trying to be chronological) :
- in case you're using a custom workspace that you've updated from v11, stop using it. Better rebuild a new v12 one from scratch.
- check the number of Undo steps and eventually lower this (mine 's set to 20).
- arrange all the palettes to your liking, then Edit Workspace. Make a change just for the sake of it, then save the workspace and have it rebuilt.
- now Quit VW in a regular manner, only then it will relaunch with the palette positions from last time.
I hope you get things working for you soon.