Unfortunatly the 7.x series of camera raw plugin is not compatible with photoshop cs5.
You could download the 7.4 DNG Converter and convert your d600 files to dng copies which then photoshop cs5 will open.
what is the downside to the DNG format? is it compatible with aperture?
I guess the major downside is instead of having just your nef files you also have to convert them to dng, another set of files, but the dng files are usually smaller in size.
As far as i know the dng files should work in aperture if you have the “Convert to Linear Image” option turned off when using the dng converter.
Also, does aperture not support the D600 camera raw files directly?