i wondered that.. resetting the PRAM? booting into safe mode and running fsck?
Quite often just resetting the PRAM can sort out a lot of problems but having to hold down the
CMD - ALT - P and R keys at the same time is not the easiest arrangement.
They should be hold down as soon as you switch on and not released until the second start up chime.
If no success the first time, try it again.
There is a complication in that you may to have reset the date and time after resetting the Parameter
RAM settings.
The friend whose machine I got going again had had the machine from someone who works for Apple
and he (the donator) had no idea about resetting the PRAM.
You might also want to run: Disk Permissions Verification and Hard Disk Verification afterwards.