Because you are using lightroom, whether cs5 supports that camera model or not is irrelevent, unless you open or place the raw file itself into photoshop.
Lightroom does not send a raw file, it sends a tiff or psd (Jpg is also an option if you use a secondary editor) file to photoshop. Odds are greater that lightroom 4 does not support your camera.
Adobe has a list of camera models that each version of lightroom and camera raw support. It will tell you whether you are up to date, need to do an update. If they are not an option then you can use the dng converter or purchase a newer version of lightroom.
Thanks very much for your reply...am now trying to update my version 4.3 of LR to 4.4. Have tried to downlaod and get a message saying Lightroom_4_LS11 disk is missing. Any ideas?
Just tried again and it now says 'the following disk images couldn't be opened - Lightroom 4 LS11 ma not recognised'