No, I haven't needed to hook the projector up again yet.

If a reboot doesn't solve it then I'll give up and just export the slides into something else.

This problem seems to have raised it's head again, this time on the monitor I've been using for months.

It's a 1920x1080 Dell, and has always worked fine until this morning when I woke the machine from sleep and the resolutions went all whizzy - exactly as before it reverted to 1024x768 mirrored. Trying to change the resolutions didn't help, as the highest possible was only 1600x1200.

I restarted the machine, and now I've got the built in LCD at 1280x800 and the external at 1600x1200, but 1920x1080 won't appear in the list of resolutions in Display Preferences, even after clicking display.

Yesterday I did do the update to 10.5.7 but I'm pretty sure that's got nothing to do with it because I had this before at uni.

I've noticed odd behaviour before when an external screen has been connected to my Mac, then the Mac goes to sleep and wakes up again, the external screen can often be fuzzy, but it's usually resolved by unplugging it and plugging it back in...

Nick, are you anywhere near an Apple store, or an Apple retailer? Either might be able to give slightly better technical advice, and they may troubleshoot for free (asking for payment if they fix the problem).