This is a Winter 14 bug. It is not yet listed in the known issues. I logged a case with SF 5 days ago. It has been escalated twice already and they are still trying to find the root cause of the issue. They still tell me 'They can't isolate the issue and are still trying to resolve'. They do however admit that is a Winter 14 bug.
I know that's not the answer you are looking for but thought I would let you know that you're not the only person getting this issue, and SF is aware of it, but the more people that log cases for this the more light will be shed on the issue, so please log cases with support for this issue