I'm in the same boat:
A little history. I had it installed on two machines, a G5 desktop and a new MBP.
G5
First tried installing on the G5. I ran the de-installer application that was in the HD/Library/Application Support/Adobe/installers folder. I checked via Spotlight and found lots of files pertaining to CS3 so deleted the via Spotlight and the Find function.
Result: can't install due to conflict.
Realized that I hadn't de-authorized CS3 so brought over the application from the MBP, launched and was able to go thru the de-authorization process.
Result: conflict with CS3
Re-ran the de-installer again with same result.
I then tried the "Clean" script provided by Adobe and got the message: Couldn't open "Applications/Adob.". Well of course, is was re moved by the other application.
MBP
Knowing about the de-autorization necessary I launched CS3 to go thru the process and was told that the trial period had expired and I had to remove CS3.
Ran the de-installer which left a lot of files that I removed as I did on the G5.
Result: Conflict with CS3.
I have gone thru the various Adobe Tech Notes but have found nothing addressing the state I find myself in now.
Does anyone have a suggestion as how to proceed.
Note: I've tried reaching Adobe Support via phone, with the obvious result - a quick message about following the Tech Note and then they hang up.
Do you think an Archive and Install might be required?
MBP 2.16Ghz; G5 Dual Core 2GHz, 2G RAM ea, 250G HD; G4 Dual 1Ghz, 1.5G RAM; Mac OS X (10.4.9) 22" LCD, 710G FW HDs, Canon: SD700IS/i850/LIDE 50, Epson R200, 30G iPod, 2G Nano