Running Exchange 2010, single server install, SP2 and currently at UR2 level.
WU just tried to install UR4 and failed (with no definitive error code), while looking through the server I determine that its currently at UR2 level (in the updates list, it shows UR1 and UR2 for exchange).
I have no idea why WU tried to install UR4, but it did and so the first thing I tried was installing UR3 which failed at the same point, telling me nothing was installed but nothing more.
I looked online and found others have had issues with UAC and UR for exchange, so I tried installing UR3 via elevated command prompt - same issue.
One of the topics I found online mentioned that when the UR install was started from a non admin command prompt, and failed, the install did actually partially install and an uninstallation was needed before retrying the install via an elevated command prompt.
Since the last UR listed was UR2 I decided to try to uninstall this and then go through the UR's in order all via command prompt, this also failed BUT what was interesting here is that the dialogue shows the following (bear in mind this is when trying to remove UR2):
So when using the uninstaller for UR2, its actually trying to uninstall UR1!
Not sure what to do from here!