LOL, I love it.... yea, no mystery cat unfortunately.
However, I did play around with locking some tabs, then unlocked them again. There is a default locked tab to C:\, but I think that's there without my doing.
I've rebooted my 'puter a few times since I first observed the behaviour (which lasted a few days) and now it seems to have settled down (the dogs chased the cats away).
Perhaps I jumped the gun a bit to ask about this issue. It coincided with the updates so I thought it was worth mentioning.
Hey, thanks again Mathias for replying and for your hard work on this project. I'm loving it and would be worse off without it. You've managed to make many people's worlds a better place. Nice one!
Oli