alyphoto, it looks like you've already gotten to the bottom of all this. I have discovered the short answer is, the problem is with the lens. I just returned from a trip out of town, where I shot a lot of stills and video footage with my T2i using an old Nikon 50mm 1.4 lens with a cheap $14 lens adapter that I purchased from Amazon.com. Just as you described on your earlier posts, this problem between the lcd image vs. your actual still, only occurs in Manual Mode. All other modes, including video, what you see on the lcd is what you capture. I swapped out my Nikon lens and adapter with my kit lens and voila! Everything is fine in Manual Mode, using the lcd.
My problem now is still not quite definitive however. I am not absolutely sure if it's a problem with the Nikon lens itself, or if it's a problem with the cheap $14 Nikon to Canon body lens adapter (there are a couple of other glitches going on relating to this lens adapter). But the T2i itself, is fine. -smile- I just have to resort to looking through the viewfinder when shooting in Manual Mode.