When I close TC, it happens sometimes, not always, that the process is still running.
So additionally, as this issue occured, when I close new instances, their process is always kept running and so after a while there can be a dozen of them.
I can start a new instance without problems, so I'm not aware of the other process, I see it when I check by with Process Explorer.
Actually, because of this new behaviour (that I only knew before as a new feature of Firefox

The only thing I changed in my "software portfolio" within the last few weeks was updating Avast Antivirus to newest and switching Windows8FirewallControl from Free to Plus Edition because the devs gave me a license as a gift for reporting bugs.