Ok what? Theme related error

I use the new Finck theme, and I love it. So here's the problem. Everytime I leave and come back it foes back to Knytt Edition. I know it can't be something too weird because I haven't changed any Firefox settings, so I don't know whats causing it. Please reply.

This happens if you sue the quick theme changer. Try changing it in your profile preferences (look & layout preferences)

Oh ok, Thanks