Update 2 :Hi,
i tried with the options you mentioned, but the result is the same. Alt+Enter does nothing, but left arrow key does.
Regards
Yannis
Update:
After fiddling around with options i activated the internal refresh rate in Madvr part in MePo renderer section and now it seems that the problem is solved (fingers crossed). If something changes, i will inform you @Sebastiii
Unfortunately same problems again. It is completely random, but i noticed a couple of patterns. 1st When i press stop to a movie and get a black screen, i can see the gui by pressing back button and then the left arrow (no alt+tab or alt+enter are working). 2nd Sometimes when i press stop, movie stops for a while and then i am getting no video but audio is continuing. At that point the only think that is working for me is put pc to sleep and resume. (stop, buckbutton, arrow keys, ctrl+alt+del, alt+enter, alt+tab are not working)