A few things -
1) CDMage will fix broken images; Make a copy first, 'cause CDMage fixes images in realtime. (sorta)
2) Did you right-click on the file to see what size it <really> is?
3) Did you try burning it? I had a 720MB .iso burn just peachy; it was only 678MB after burning; Quite a bit of that info is 'instructions' of a sort for your burner.
Aaaand, last but not least, if you decide to burn it, just hit the simulation button first. Most burning apps have a simulation option. Works every time.
P.S. Even if it is too large to fit onto CD, any virtual drive should read it just fine after CDMage is done with it. It may end up bigger or smaller, though...