Double File Extension

I have a problem with autofilename, where I write filename.pdf to the registry and it appears as filename.pdf.pdf on the disk.  On one system it works as just filename.pdf and the other has the double file extension.  I can not figure out the difference.

The following link also saw the issue, but I can not open it:

http://www.pdfforge.org/node/1163

Does anyone have a suggestion?

Thanks,

Joel