We’ve posted Disable VM Buffering, an optional plug-in for Photoshop CS2 (Mac only) that addresses painting pauses on machines with more than 4GB of RAM. From the ReadMe:
The Disable VM Buffering plug-in can be installed to eliminate pauses during painting on Macintosh machines with more than 4GB of physical RAM installed. It will have no effect on machines with 4GB or less of RAM. On machines with more than 4GB of RAM it can eliminate pauses during painting operations at some cost in performance with very large documents.
More details about the plug-in and why you may or may not want to install it are on the download page.