I see you've had no replies to your post yet, so I wanted to give my two cents. You can Google this issue and find a number of reasons for this problem, but your best bet would be to get to a mechanic and let them diagnose your issue. People here won't be able to give you solutions considering the number of reasons that orbit the problem and they can't physically diagnose it. We can all speculate. I know this wasn't an answer, but I didn't want you just dying on the vine in this forum without a response.
Good luck with your issue and I would personally like to know what the problem was, so if you don't mind posting back with your findings, it would be greatly appreciated.