I am pretty sure it's because this them was for 3.6, and not 3.7. (they have added some security tokens in 3.7 it seems) I will look at either fixing it or putting in a new theme tomorrow.
I get that off of control panel top link every time too on Firefox 2.X, but i can still go through my inbox like i usually do to get there though.
ok im setting it back to the default theme for now... sorry guys, but a working default theme is better then a broken custom theme. We will try to get something else up tomorrow.
I don't think anyone was using the search and people like the custom theme so I don't know if it was worth it to go back