i don't wuite understand? it works but it doesn't work? do you mean it does not work with the stock "camera" app? what happens when you open the camera app and hit menu, then "switch cameras"???
This is more informational than helpful, but I just opened my camera and took 3 very bad pictures of myself with the front facing camera with no problems. Have you done the usual shut down, pull battery, replace battery and reboot? That usually works when mine is doing something weird, like when it suddenly forgot it had sound capabilities and all of my reminders stopped working and the phone wouldn't ring.
It can be a little finicky at times, but at least it isn't boring.
This has happened with me a few times. Here's what to do:
Menu-->Settings-->Applications-->Manage Applications-->Click the "All" tab-->Click "Camera"--> Then click "Clear data"
After that you should be good to go, if it happens again down the road repeat this same process. Please mark this as solved if it fixed your issue.