When attempting to open a workflow .package file from an external source, (which is the best way to transfer Workflow projects), the following Unexpected Exception, Size Mismatch error occurred, as shown in the screen shot. This error caused frustration, as no matter what I tried to get the .package file to open, it would not. Why? 

Well, lets first understand that the .package file is essentially just a zip file, and the file can be renamed to have a .zip extension and then extracted using standard ZIP utilities. Most of the time that will work.   In this case however,  the .package file was more than likely scanned with a virus scanner during transfer, and certain files contained in the package file probably were flagged by the virus scanner, and were removed from the .package file.  When the check sum process of extraction occurred to open the package file in Workflow, it was determined that the file counts and sizes were incorrect, and thus the package could not extract and load successfully.

Ultimately, the package file needs to be re-transferred, without any third party application interference.