Jpegs opening in Raw in CS-3
I think that if the file has previously been opened in ACR, PS will always open the file in ACR regardless of the TIFF/JPEG switch setting because it flags the file with the ACR settings you made at the time.
The only way I can think of to stop it would be to open CS3 Bridge, right-click the file >
develop settings >
That would of course, remove any changes you had made in ACR.