computer typing zeros

Its spooky to open a window and see G5 typing zeros. It has happened when i've tried to type and it takes over . . . but its also happened when i havent even touched the keyboard , like today i just opened a Textedit old document and it started generating zeros at the beginning of the doc .

Shutting computer down and doing a Safe boot has helped....but then
its alright for awhile and then it starts again . It's very random.Sometimes it can function ok for 15 minutes and then goes weird . sometimes even doing shutdown/ safe boot doesnt help.

When its malfunctioning like this , its impossible to Select anything .eg
couldnt select a file or application thats further down in the Finder because it flickers and jumps to the first thing on top

Have tried Repairing permissions a few times - no help
Luckily i have this other computer so i can put out this Help message !
any suggestions most welcomed !

Sounds more like a firmware or more likely hardware issue in the keyboard to me. Have you popped the 0 key off to make sure there isn't anything under it?

Agreed! Sounds like a stuck key to me.