Paypal Std drop-downs blanked out?

I'm sure there must be a simple answer to this. The drop-downs on the Paypal Std are blanked out and no matter what I do they won't appear. Anyone any ideas?

The email address is in, selected to sandbox or not (nothing changes), transaction method sale, debug mode enabled, total 0.01.

I should add this is with v1.5.3.1.

Just in case anyone else has this problem - it appears to be due to a database corruption.