Never heard of the software you used, but you can get TMPGenc at http;//www.tmpgenc.net. There are some guides to using it at
http://www.vcdhelp.com. I have read that sometimes loading the most recent DivX codec you can find will fix the problem you described. I'm not really into DivX so I can't provide any better details.
http://www.divx-digest.com and
http://www.doom9.net might be good places to get DivX info. I have read about a few desperate guys who fed their DivX downloads into Virtual Dub and used Virtual Dub to flip the video image prior to encoding. That's an advanced task and might be too complicated for you to do, but if nothing else works you can try that. I think Virtual Dub can be found at
http://www.virtualdub.com (not sure about the .com part - try .org or .net if you can't find it. Doom9 should have a copy in the Downloads section.).