Can’t access permalings admin page

Hi there.

I cant access the permalinks page in the admin panel. When I try to go to the page the admin menu loads fine, but everything below it is just blank. No error messages showing, so I have no clue about where to look for a problem.

Anyone got some ideas on what to do? or just some thoughts on what could cause such a problem?

Its a heavily modified theme, but I havent touched any core files (I think :P)