BSOD Worker thread returned at bad IRQL

Hey guys. So yeah, I got a BSOD called: WORKER_THREAD_RETURNED_AT_BAD_IRQL I've had this BSOD atleast 10 times in the last month or so, and I think it started when I installed CCleaner and left the checkbox of delete bad registry keys on. (not sure how it's called, but it delete registry items without a value, I guess) I've used this program regularly on my old computers and it did his job...