I think you may be a bit stuffed.
The way the really old Cool Edit works is that it records tracks to a temp file which (as you clearly know) you then have to Save to keep permanently. The temp track is a Wave file which, depending on your settings, could be pretty huge after 4 hours. I haven't done the mental math but it could be pressing up against the maximum file size allowed by Windows. Then saving to MP3 would require a LOT of processing.
The only thing I could think of would be to try playing the MP3 file in some nice, forgiving simple player. If, by good luck, you can get it to play without skipping, you could then record it back into your DAW.
For the future, a couple of suggestions.
First, if you can possibly afford them, current versions of Audition don't mess with temp files and, once you specify a title, record direct to disk.
Second, if you continue working with CE2.1, recording in Multitrack rather than Edit has a facility to roll over into multiple files if the sizes get too big for Windows to handle.
Sorry I can't be more help.
The pessimist sees the glass as half empty. The optimist sees it as half full. The realist just drains the darn thing and gets a refill!