Recently I've been having the issue where if I shut down Firefox and then try to reopen it after a period of time, it'll complain that 'a copy of Firefox is already running'. When I open the Task manager and check the running processes, I find Firefox eating up my resources.

This issue is beginning to become a large hassle to deal with, so I'm wondering if there is a fix of some sort? I did find the exact same issue in another thread, but it's fix didn't apply to me as I didn't have the problematic Add-on that was thought to cause the issue...