I just did an upgrade from tiger and have had no issues at all. Guess I am one of the lucky ones. A few questions:
1. Have you done repair and verify permissions from the DVD?
2. Do you have any 3rd party apps that could be causing the problem?
3. Hacked any part of your OS?
4. Did you try downloading OnyX? Great program!
5. Using cheap RAM? Take out your RAM and reinstall the RAM that came with your computer.
Hope this helps you...
1. No, have from disk utility in leopard
2. no
3. not had time, and no.
4. Have the tiger version, haven't tried the newest. Suggestions for use?
5. Stock ram