As far as I know, Photoshop was/is the key application in connexion with suites, so maybe the Photshop serial number is the one needed when you have upgraded from individual applications to a suite.
It seems that helping you get the CS2 reinstalled is the opposite of helping you.
I have the same problem, I too have reinstalled Illustrator, you say install photoshop will give that a try now, however researching online could be something to do with font problem or font cache. The problem only occurred a short while after I installed a new adobe upgrade that came up on updater,
any ideas would be great as I am starting to tear my hair out not being able to use illustrator
... you say install photoshop ...
What I am suggesting is your using the serial number from Photoshop. Upgrades are full versions, so the old versions are not needed; they may be nice to have, though.