I had Photoshop 7. I upgraded to CS2 Standard Suite, as I have the occasional need for Illustrator. I did lots of tutorials, and everything worked.
A couple of months ago I bought a new G5. I deactivated the CS2 stuff, uninstalled, and then installed and activated on the new box. I use Photoshop all the time and it's fine. I haven't used Illustrator for some weeks. Yesterday I needed it and it wouldn't run. No error message, nothing. Just plain won't work.
I assumed it was an activation thing, but the Adobe site tells me one activation works for the entire suite. I tried re-installing from the disc, and it says it can't as it's installed already.
After clicking on the icon to boot Illustrator, immediately hold down shift command alt. You will be asked if you wish to reset the prefs, click ok.
If that does not fix your problem, you may have some Mac OSX security issues and can run the disk utility, in your applications folder, then click on the fix permissions button.
If still not working do a fin for .lst on your drive. You can delete each one of those by commadn delete on each filename in the results. Those files get corrupted occasionally and they regenerate themeselves so trashing them is ok.