I'll post this in here as it's probably nightly related as it's only happened today.
Twice today, I've had the screen go completely black apart from the notification bar. There was a sync icon, but if it was syncing, it was doing it for ages.
Home button didn't respond, although a long press did bring up my used apps list. Lock screen would appear ok, but after unlocking the screen would still be black. A reboot fixed it the first time, but after the second my phone stayed stuck at the G1 screen.
I don't remember what I was doing the first time, but the second I was trying to set a live wallpaper (long press on home screen, wallpapers, live wallpaper, first time it brought up a black screen, then went straight back to home, second time the screen stayed black).
Before anyone asks, no, I don't have a logcat because I'm an idiot

, but I'll get one if it happens again.
I also don't seem to be able to restore my last nandroid backup, the dots just keep coming.
Wiped first, now I'm booting again.
Except I'm booting over and over again
Flashed the original CM6 RC1 and I'm back. Will finish messing when I get home.