Today I ran Setup for the CU2 update to Exchange 2013 on a standalone server which previously had CU1 installed. And - mea culpa - I didn't do as much pre-install reading as I should have done. I double-clicked on Setup and followed the wizard, but it failed with an error "Specified Cast is Not Valid".
I found the following pages that looked relevant:
The second of these states that before running the GUI setup for CU2:
a) You need to run a Schema Update
b) You need to run an AD Update
c) Best practice to put the servers into Maintenance Mode.
I didn't do any of these, I just ran the GUI setup.
So now I have a completely non-functional production Exchange server, which is a major problem.
Looking for advice, please, on how I can move from the current situation to a working server with the CU2 update installed.