Dear All,
Yes, indeed, this is a TeensyDuino support since I am busy with some projects with it as well. It has been installed with its own built in installer, so Board Manager wasn't used for that.
Maybe I am wrong but I don't think that it influents the generic Arduino boards routins somehow. However everything is possible, I could investigate it by removing of the Teensy staff still today in the evening only as I am at my work now, not at home. I will let you know the result.
What I did so far as a temporary solution - in Arduino icon properties I re-assigned its path to the exe file extracted from zip archive and it works fine so far. I understand that this is a very straight forward solution however it helped me to program a few Attiny85 chips I urgently needed yesterday.
If you're happen to find out what's wrong with the normal way of IDE working - this would put my mind on ease now worrying that at certain moment an unexpected crash could happen.
Many thanks!