WSUS Snapin MMC Fails To Load

An interesting error today, where my WSUS console kept crashing and failing to load the snapin.

Running it with the 'RUN AS' elevation gave me partial access to the system but only to the computers list - not the updates.

The Event Log recorded the following error;

The WSUS administration console has encountered an unexpected error. This may be a transient error; try restarting the administration console. If this error persists,

Try removing the persisted preferences for the console by deleting the wsus file under %appdata%\Microsoft\MMC\.

System.ArgumentException -- An item with the same key has already been added.

Source

mscorlib

Stack Trace:

...etc...

The actual issue turned out to be that the user who installed the console originally, was no longer in the domain admins group. Adding the user account back into Domain Admins and trying again worked without issue.

Obviously this isnt a permenant solution but does solve the reason why.