When I download premier movie avi files (DVDRip types only) they are not recognized by any of my media players or conversion programs. After sveral months pass and newer versions are downloaded, they work perfectly.
I've tried every solution that I could think of, but none worked.
I would appreciate any suggestions as to what the cause might be and how to remedy it.

It sounds like the files may be Fakes. IMO AVI files are the chosen Video File Extension on the Gnutella Network.
What Media Player and Conversion program are you using?? It could be a Codecs issue with the Player. If you think that they may be Fakes see instruction below.

Have you tried checking the Files with Bitzi before hand??

This is how it works. After you have completed your search, Right click on the file that you're interested in. Now go to Advanced > Lookup File With Bitzi. Left click on that and a new browser window will open which is Bitzi. Now you will see how other members have rated this file. If you see something like "Bitprint not found" then Leave it alone. Its probably a Fake or Corrupt File. If it has been Rated then you can read what or how the members feel about the file.

__________________
I Don't Suffer From Insanity, I Enjoy Every Minute of it

Thanks for the info. Your assumption was right on the money! The file is not only a fake, but is also deemed dangerous by three sources.