Sergey,
thanks for the link. In reading the doc below the download link I see what might be the problem. It says:
If you 'SET LIBRARY TO vfpencryption.fll' in Visual FoxPro and get an error saying that the FLL is invalid, then you (or your client) don't have the required C runtimes installed.

I installed Open Office a few days ago and I'll bet that it installed new C runtimes that overwrote the ones that the old version needed. OK, just a guess but I think better than a 60% chance that's it. What do you think?


>The newer version is available at http://www.sweetpotatosoftware.com/SPSBlog/PermaLink,guid,5d4a0cf0-7d1d-4353-a49b-667946ff1c81.aspx
>>>
>>The program now works fine but what could have caused the .FLL to suddenly become invalid after working for some number of months. As I said, I have confirmed beyond any doubt that it is the same .FLL file I had run for some time.
>>TIA