I would certainly have asked the Apple genius what he/she did to 'fix' the problem - it was obviously not a permanent fix... I've read a few threads here about runaway Dock's. Can you just kill the process and then Force Quit the Finder? There's no chance of doing any damage to your computer but the process should not be consuming 95% of your CPU.
It's likely something simple - particularly if the genius was able to offer a quick fix. Take it back and let them walk you through the fix. If you're not satisfied that the fix will remain 'fixed,' by all means get a new machine.
Just my opinion,
Try running your laptop under a different user. I had the same symptons and the genius concluded it was software related.
I added a new user account and that seemed to show no problems, so I deleted my normal account and recreated it and everything seems to be running fine now. The other suggestions I've seen have been:
- Changing your desktop wallpaper
- Removing the date from the menu bar
Likely all the Apple shop assistant did is either force quit the Dock in Activity Monitor or type
The problem has recurred because he/she didn't search for and eliminate the underlying software conflict.
To start with, remove everything from here:
> System Preferences... > Users & Groups | Login Items
by selecting everything in the list and hitting the minus '-' button undereneath the list.
Restart the mac and test.