Hi guys! I had the same problem before and the reason behind that was I installed kernel power 46 (you'll also have the same problem on kp47) on an N900 with an incompatible version of Fcamera/BlessN900.
What you should do is uninstall Fcam or BlessN900 and then reinstall it, it should download the latest Fcam driver which is compatible with kp46/47.
Hope this helps.