Electronic Noise when saving JPG

[MamaGrouch]

Ok, this is driving me crazy and has gotten so bad I don't know what to do.

I am post-processing photos from a wedding that I just took using my 5dMarkII in photoshop CS2. I took the photos in RAW and am saving them as jpg after processing.

In photoshop they look smooth and perfect, but when I look at them in my faststone image viewer afterwards they are completely grainy and full of electronic noise. It doesn't seem to be tied to my ISO settings at all. I am wondering what is causing this? I am going to give you three screen shots (one in photoshop and one afterwards and one actual "saved as web") to see if anyone can please help me. I have never encountered this before. Also, when the file is "saved for web" (which I do with all my photos as well) there is no electronic noise and it looks exactly like it should.

"help me" - is the photoshop screenshot
"help me noisy" - is the faststone image viewer jpg screenshot
"S and E (226-1)" - is the actual smaller "saved for web" file that has no noise

I am thinking (since this has only started happening since I got my 5d) that it has something to do with the size of the file/outdatedness of my photoshop/something along those lines? Thank you for any help you can give me!

[OsmosisStudios]

I would guess it's your image viewer re-scaling the image weirdly.