my monitor suddenly goes to sleep and I can't wake it up

The monitor suddenly goes to sleep, and I can't wake it up again.
Gustavo Gomez wrote on :

I have a powermac g3 desktop, running 10.2.8 with classic 9.2.2. This has happened about 6 times, and it always happens while running a classic application (If I remember correctly the applications where Arthur's Kindergarten, Blues Clues ABC's, Mia's Reading Adventure, and this last time was when starting up classic). The monitor suddenly goes to sleep, and I can't wake it up again. Sometimes I can ssh to the computer and I tried killing classic and killing the Login session, but the monitor keeps on sleeping. Sometimes I can't even ssh to the computer. The only way to fix it has been to restart. There is nothing reported by crash reporter or in any log.

help!

-ggem.

P.S. yes, this started after I installed the 10.2.8 upgrade.