I’m getting sorts of problems initially described in this thread too after the latest (free) program update, with a popup proclaiming a Browser add on is a problem. Clicking the button to clean, but runs for ages before it freezes, becoming unresponsive. Being unable to stop it, restarting the PC takes several goes after that. Then it settles. It did the same today after the update yesterday.

Regarding cookie settings in Firefox, I have always had accept third party cookies enabled. Not really sure what having them disabled will do, or not do, or is the halfway house of visited best? So many sites ask you to accept cookies now and some rely on them (Quidco).