PDF Merge - Unknown Error

[cjblckwl82]

I am getting a weird error message on something that I have been able to do in the past.
If I select 2 PDF files, right-click --> PDF-Shell Tools --> Merge/Rearrange Pages...

I get to the Merge Screen and I see my PDFs listed but when I click run at the bottom, I get an error message.
The error says "Operation failed - Unknown error" and then the path to the PDF files.

I can click cancel or ignore, if I chose ignore, only one PDF file is in the new "merged" PDF file.
Any ideas?

[RTT]

Make sure you are using the current 3.3 version.
How many pages has each PDF? Are you merging all the pages, or specifying a range?

if you can, send me these two PDF, attached to an email, so I can try it here.