It seems that some Users of Outlook 2010 experience a runtime Error in GpgOL.
They report, that the GpgOL Plugin is correctly displayed in the frontend, but it doesn't do any work. They can't en- or decrypt, sign or check signatures on mails. Neither does the display of GpgOL change away from "Insecure".
In addition to that following error pops up:
Fehler bei benutzerdefinierter Benutzeroberfläche von XML von GpgOL - The GnuPG Outlook Plugin Zeile: 1 Spalte: 769 Fehlercode: 0x80004005 Unbekannte Office-Steuerelement-ID: TabComposeTool"
A user states, that it seems that the menu ribbon integration seems to fail:
(The original reports can be found via the External Link)