If you track the problem down to an IIS issue in which the WSUSPOOL keep stopping, you likely need to expand the memory limitation and the recycle time:
- Launch IIS
- Click on APPLICATION POOLS
- Click on WSUSPOOL
- Click ADVANCED SETTINGS (action pane on right side)
- Scroll down and increase the PRIVATE MEMORY LIMIT and decrease the REGULAR TIME INTERVAL.
The screen shot below shows the setting we are using at one of our clients:
See our short explanation of how to fix SOLVED: WSUS Reset Server Node .