I have an open ticket with support, and this bug is supposed to be fixed in the next build. It has a tentative release sometime in February. I'll test it and post the results as soon as it is available.
There are 4 workarounds that I'm aware of, but not all will be acceptable based on your use case and policies:
1. Disabling desktop notifications in Outlook
2. Using Outlook in Cached Mode
3. Installing PGP without the MAPI plug-in
4. Removing PGP from Startup, start it when necessary for ad hoc tasks, and exiting immediately.