Originally Posted by
Cinno
Move the character data folder to your desktop, and then login as usual. The game will automatically create a new data folder for that character with all the settings and ui stuff at default. If it runs without the issue, then you can be pretty sure that the problem is probably the character data folder.
If that ends up being the case, you could probably move files over from the old folder to the new one one by one, to figure out what exactly is causing the issues, if you had the patience for that.
But yeah the fact that its only affecting one of your characters does really point towards it being an issue with that folder. Worth a try, even if just to rule it out.