Right.
Canon 5D MkII support was introduced in Adobe Camera Raw version 5.2. Unfortunately this is only compatible with Photoshop CS4 or later.
You can use the Adobe DNG converter. This is quite a good way of doing things but is an extra step before you pull your images into Photoshop.
So the workflow in this case is RAW 5DM2 files -> Adobe DNG -> Photoshop.
Yes you can use Lightroom v2 or v3 Beta. But really moving to Lightroom is if you want to change your workflow. Don't be frightened by Lightroom - when you go into the 'Develop' module it's practically the same as opening RAW files in Photoshop. The image change options are the same and actually driven by the same software.
What do you actually want to do in Photoshop? If all you do is a quick levels tweak and crop / straighten / sats etc then you could just do all of this in Lightroom then export (the same as 'save as' in PS) as JPEG or whatever. If you do some serious curves, dodging / burning, cloning then you will need to pull back into Photoshop anyway.
Back to the original problem:- My advice is one thing at a time. Download the latest Adobe DNG Converter. Run it on the files from your 5D MkII. Then process as usual in PS CS3. Once you have that sussed think about Lightroom if you need it!
HTH
Mark F
