I use Bridge CS4 because I prefer it to bridge CS5 but when I edit images in ACR in bridge cs4 and click 'Open Image' I want it to open automatically in PS CS5 and instead it opens always into PS CS4. In preferences>file type associations, everything is set to CS5 so I don't know how to direct opening images from ACR to open in photoshop CS5 not CS4. I've had it working on a different system but I don't remember what I did to get it to work.
Uh huh...and why would you expect CS5 to open the image from Bridge CS4? You haven't stated why you are trying to use Bridge CS4, but as you've found out, that is not an optimal solution....(BTW, troubleshooting 101 dictates that you at least mention what platform and OS you are using).