You can use a couple of indirect methods, just not direct Project Save/Save_As. Look at EDL Export, and AAF Export, or do a rough cut (do not cut tightly, as you will loose your Handles, and do NOT add Transitions for the same reason), and then Export the Timeline to say Lagarith Lossless, or DV-AVI Type II for Import.
Thanks Bill. I was trying to avoid the EDL path as it's a large project and i don't want the client to have to put the multilayered EDL back together.
Can't go the export path as they need full access to the edit. I guess there is no easy way.
The only way would be the upgrading of CS3 to CS5.