I'm back asking this question because I still haven't got the answer I was looking for... so I've been using PS on my PC because this grey'd out thing is confusing me.
Here's a typical scenario. I put a SD card from my camera in my USB card reader and I can see all the files. I open PS and then select file, and browse to the image I want to edit. I open the image in PS, edit it, and then save it for web. Now I want to use that modified jpg in my Photobucket account, so I go to photobucket and select upload files, browse for that specific file, and it's grey in the stored location so I can't access it. Do the same exact thing on my PC and I can access it. What gives, and what makes it so hard to deal with images on a mac? I'm baffled because I always thought it would be easier.