PGP Viewer always tries to open PGP Zip files named Attachment*.pgp
Could not save attachment
This behavior is related to PGP Desktop 10.x which introduced MAPI proxies.
It is by-design behavior and PGP Viewer intended to open all .PGP files with name matching *attachment* pattern, regardless character case in their names.
I.e. files named "Attachment", "Attachment", "Attachment", "Attachment from John", "My old attachments from 2009" and others files with .pgp extension containing word "attachment" in their name, will be opened in PGP Viewer due to application design.
Do not name PGP ZIP files *Attachment*.pgp
Rename attached file when saving attachments from incoming mail in order to open them with PGP ZIP.
For example rename "Attachment" to "SomeFileName.pgp".
PGP Desktop 10.x