iSight camera not detected after sleep

Hi,

The iSight camera on my 9 month old MacBook Air has decided that it will no longer be detected after the laptop has been asleep.

If I log out, then log back in again, it is then detected and works as it should do. It only appears to affect my user profile (I've created a test profile, logged in with that then put the machine to sleep). I've also repaired permissions on the disc, and reset the PMU, all to no avail. It is listed in the System Information under USB. It affects all applications that use it. I've run out of things to try, short of going to my Apple dealer to get them to sort it out, or deleting my profile and setting a new one up.

One other thing, which may be related, is that the screen dims after 30 seconds, despite the power settings set at 3 minutes for the screen to sleep at.

I have Mac OS X 10.7.4 installed (which has been updated by the system a few times...I think it had 10.7.1 when I first got the machine), but these problems did not start following any form of upgrade (as far as I can remember).

Thanks in advance,

Gerald.