Hello!
I'm sorry to hear that re-installing OS X didn't solve the problem.
Apparently the solution to it, seems to depend a bit on the Apple model you're using...
You could also try this (which I did, and solved my problem the first time!):
You could reset your Mac's PRAM!
1. Turn computer ON;
2. Immediatly after, hold: Command + Alt + P + R;
3. Your Mac screen will flash and you'll hear a sound twice!
4. Let go of the keyboard and let your Mac restart alone!
This also seems to do the trick to most users!
Also, you could enter in your Mac with Safe Mode (Turn it ON and hold Shift key, until an horizontal grey bar appears on your screen!) then use Disk Utility, with the OS X working, to repair anything you might need reapired! Then reboot your Mac!!!
For some other users, that did the trick!
NOW; it's my turn to make a question: anyone of you was able to upgrade iLife, iWork & Aperture, for free??? I bought those bundles when they were sould in boxes, and can't seem to upgrade for free...
Hope my suggestions help!
All the best!!!