The Plugin Site

You could try moving all third party plugins (not the Adobe ones) out of the Plugins folder and see if Photoshop CS3 works now.

You should also make sure that some Adobe plugins from CS2 are using CS3. This can cause problems. This can easily happen if you installed Photoshop CS3 in the same folder as the old CS2 installation or if you have set the plugin path in the CS3 Preferences to the old CS2 plugins folder.

But I think the problems has more to do with Photoshop itself than plugins.

The PS CS3 beta had problems with a flickering/disappearing cursor; I haven't tried the final version yet so I don't know if it's an Adobe thing or a plug-ins thing.

As for CS3-compatible plug-ins, I've begun putting a "CS3 ready" button on the relevant plug-in pages on my site (scroll down on this page for an example).