Citrix Provisioning Server 5.6 SP1. While changing the Mode on a vDisk, I received the dubious ‘An unexpected MAPI error occurred” error shown below. The details show information related to an inability to mount the vDisk and a driver related issue.
After some Googling around, I found on the Citrix Forums, a thread that stated that while there is no FIX for this issue, a temporary work around is to switch the Licensing Properties on the vDisk to none. This will allow you to change the rest of the options on the remaining tabs.
Hopefully, this will be addressed in a future hotfix but for now, switching the licensing to None is a solid workaround.