When I run CCleaner, it tells me it can't clean Mozilla Firefox cache until it is shut down -- but it IS shut down. Please advise. Thanks.

Hi Bostonboy and welcome to the forum.

Have you checked Task Manager (Ctrl-Alt-Delete), to see if it's still running as a process for some reason?

No, that didn't work. But I figured out that if I reboot and run CCleaner before I open Firefox, it cleans Firefox caches. I think this has to do with a bug other firebox users may be experiencing that gives you an error message when you close Windows.

When you close Firefox, it may actually take a while until it's completely shut down, especially if you have used it for a long time. It cleans up a lot of things while shutting down; that's why it takes a while.

Wait two or three minutes after closing Firefox, and you should be able to get the cache cleaned.