How to kill stuck active task in Profile Manager?

Hello,

So my Profile Manager has stopped working and I thinking now that it might be due to a task that I cannot cancel.

The task is trying to push settings to a device relative to a user that does not exist on that device anymore. I am not sure if that is the problem, but when I try to cancel the task I get this error:

A Server Error has Occurred

Please reload the webpage and try again.

If this error continues, please contact your administrator.

Maybe I can try un-enrolling the offending machine or should I be looking at something else?

Thanks

Morgs