Taking between 5 and 20 minutes before start up chime.When it's running - everything seems fine, but my Mac Pro takes an age to do the self test, sometimes it doesn't start at all...
Answer to: Taking between 5 and 20 minutes before start up chime.Fixed it!!! The answer was corrupt firmware. The apple firmware recovery tool (intended to rescue bricked machines due to firmware flashing failure) ended up fixing it. Never seen anything like this on a Mac before.