Going from Lightroom to CS5 it wants to upgrade to Camera Raw 8.4. I'm not getting all the info together to be able to figure it out.
Photoshop CS5 has a a maximum version: CR 6.7 see: Camera Raw-compatible Adobe applications
So you can not use the RAW images from camera's that need the support for > 6.7 version of RAW plugin. see: Camera Raw plug-in | Supported cameras
You can as a work around use the free DNG convertor convert the RAW images to DNG, DNG is supported in all versions of Photoshop and Lightroom.
Thanks very much!!!