After installing V2.11 Tixati is now irresponsive, it continues to download but the menus, settings, etc are almost impossible to configure, it stalls and I have to wait until something happens. V1.99 was working fine...

I never experienced anything even close to what you describe with any version of Tixati, but I actually did experience a slight but noticeable performance improvement in the user interface response times after upgrading to 2.11, in one of my older machines. It feels smoother and slicker now.

Just in case, you could try completely uninstalling and reinstalling the new version (make sure to safeguard your .torrent files first!). If the issue persists, try temporarily disabling your anti-virus resident protection to make sure it's not interfering by means of automatic analysis of Tixati's executable and memory process when you run it.