Here is a quick tip for early adaptors of Adobe CS3. If you want to install both CS2 and CS3 on the same Mac, make sure you install Adobe CS2 first. If Adobe CS3 is already installed, the CS2 installer will gray out Acrobat, Illustrator and InDesign, thinking those applications are already installed.
The simple, but frustrating solution is to uninstall CS3 and reinstall CS2 first.
Source: We're throwing in an extra CS3 tip each week for early adaptors. For CreativeTechs' current rule-of-thumb on when to upgrade, we've published a short tip: When to Upgrade to Adobe CS3?
Update: As many (many) readers pointed out this morning, we had a typo in the first version of this tip. Thanks for the sharp eyes! Should be fixed now.