Go into the add-in manager and turn off that third party plug in. Third party apps can cause outlook to do very weird stuff.

Including profile corruption. Delete all of your old profiles, and then create a new one. I've actually seen the registry hives for outlook profiles get corrupt so if you just creating a new profile sometimes even that will not fix the problem.

So if just creating a new profile doesn't fix it, delete all profiles, then try creating a new one.