[Cin] MKV containers

[Andrea paz]

Even if I managed to install CinGG, the playback problems remain. With
mkv the problem is more serious but the other containers don't work
well anymore. Watch the video:
https://www.dropbox.com/s/hf3hd80dqja08jz/playback.mp4?dl=0
There is a first slowdown at the first wipe transition, then slowly
the playback resumes fluidity. At the second transition the insertion
point slows down a lot, so much so that it seems blocked, while the
audio continues to flow normally.
This happens to me every effect or transition I put on, and it gets
worse using mkv (with any codec below) which slows down even simple
playback without effects.
I don't know when this problem started, but no less than a month. I
don't even know if it's due to my PC. Surely it had never occurred
before.

Notebook i7 2720QM; Geforce 460M, 12 GB RAM, SSD;
Checked "Play Every Frame";
Video-driver: X11-OpenGL;