[G4] Mystery startup problem

[John Collins]

Any thoughts?  I have solved the problem but can't understand it.

I was working with iDVD5 to reconstruct a video project which had been 
corrupted by changed file locations, etc. And iDVD froze, I finally 
force quit and then had other problems like the mouse failed, I plugged 
in hard wired mouse with no success, did a complete restart and the G4 
QS/dual800 restarted from a different disc.The mouse was then OK. I 
tried several times to reset to the primary startup disc and could not 
get any success.  It would not restart from that disc--it showed up as 
a viable start up option but would then start from a different disc. I 
used Disc Warrior and Drive Genius (time consuming and not sure it did 
anything--scanning showed no bad blocks on the disc). Disc Warrior also 
indicated no problems. It would still not restart from the primary 
start disc.

Finally in desperation, I cloned (carbon copy c) the primary start up 
disc to a clean disc--thinking the original OS X.3.9 was probably 
corrupted and I was pretty sure it would be a waste of time. 
Instead--it started up fine from the cloned copy. So I figured it must 
be a problem with the hard drive. I erased the original drive and 
recloned the copy back to it and all is well. As far as I can tell all 
is as it originally was.

Any similar mysteries or thoughts?

John in Tucson