It deletes urlcache - no big surprises there

It gets rid old cached root authorities, to make way for new root authorities.
Window's new higher security requirements are that third party software like AVG requires athorisation in the form of a root certificate before it can run or update itself on your computer. It looks like it is being denied that because you still have the expired root certificate in place and it needs to be manually flushed out before the new one can be installed.
In theory this should happen automatically and a file called
authrootstl.cab is downloaded in the background and this enables 3rd party software to run for a limited period until it gets renewed again.
You may want to have a look in Event Viewer in Adminstrative Tools to see if you have an error relating to:
Source: CAPI2
Event ID 4107