The same problem with Kubuntu 7.10
Driver "radeon"
Card Radeon 9100
Temporary solution :
1. CTRL+ALT+F1 (go to console)
2. ALT+F7 (go to X org)
Hint:
Driver (?) didn't set up proper resolution/refresh rate ,
when changed in display settings (even to the same param.)
after confirm to change resolution screen goes black and monitor turns off.
Confirmed.
The same problem with Kubuntu 7.10
Driver "radeon"
Card Radeon 9100
Temporary solution :
1. CTRL+ALT+F1 (go to console)
2. ALT+F7 (go to X org)
Hint:
Driver (?) didn't set up proper resolution/refresh rate ,
when changed in display settings (even to the same param.)
after confirm to change resolution screen goes black and monitor turns off.
Want more information?
Best regards
Cactus