Password-protected PDFs making mail blank view of messages?
Surreal problem that seems to have started about the same time as my 10.8.4 update (from 10.8.3):
Viewing the standard Mail view, with mailboxes on the left, message list for the selected mailbox in the middle, and message text in the largest pane on the right of the window; when moving through the list of messages, moving down and seeing the message texts to the right, all of a sudden, the preview pane to the right go BLANK. And I've narrowed it down to several suspect messages that came from a regular group of business contacts who send me reports as password-protected PDFs. I prepared a test PDF with Preview, encrypted, and used that to test the proposition that password-protected PDFs are what is 'breaking' the view of message contents in the right hand window, and it is clearly the problem.
After I view a message with the gray password-protected preview image showing in the preview pane, switching to another message in the message list, that next message shows a normal header but the text/body of the message shows blank. And then the next messages keep showing blank until I either: hide and unhide the main mail window OR quit and reopen mail. But double-clicking on any message in the list to open it properly in its own window shows it normally.
Rebuilding my mailboxes did not help. Rebooting did not help.
Any ideas about what the heck might be going on?
MacBook Pro, OS X Mountain Lion (10.8.3)