In my case I think it had something to do with Canon printer software. Do you have a Canon printer? The software that came with the MP830 did it to me.
Thanks - no I don't - I've never attached a printer to the macbook, nor any other printer software at all - nothing shows up on Activity Monitor In fact the Activity Monitor when on is using most CPU of all!
The only thing I can think is - from it's behaviour - its something to do with flash when using browsers... but that's a dorks hunch nothing more
OK, something is very wrong. Activity monitor is showing 50% User CPU usage when nothing is running. By way of comparison, the other computer is only showing 2%.
Thanks, this thread was awesome. My daughter's MacBook Pro fan was on all the time and I downloaded Macs Fan Control and saw that both fans were running at the same speed but the temp was in the 80's and checked the Activity Monitor and saw that an old printer driver was hogging CPU time. I went into my System Preferences/Printers and deleted the printers we were no longer using on this Mac, including the one that was hogging CPU, and the fan immediately spooled down and now the computer is running quietly again!