I did some more playing with this. On one of the computers I fixed the problem by picking one of the defualt DNN skins. Now the buttons on the move thread page work. I can now choose which form to move to. On the other computer I tried the same thing, but it doesn't matter what skin I choose, it will not let me use the button to pick another forum.
The buttons on any of the admin pages do not work either, such as picking security roles and such.
The error I get is the same as above except the line number changes.
I'll keep playing, if I find anything else out, I'll post it.
Thanks