MKV playing fast, skipping seconds and gets stuck

[zappaz]

When i try to play 1080p mkv files with DTS in BS Player pro, i get crappy sound and video is skipping seconds and playing way too fast, it also gets stuck a lot.
I installed all the codecs which bs player said i was missing.
Also tried the CCCP pack for mkv but still the same problems.

Strange thing is that i played the same file a few days ago with BS Player, and there were no problems at all.

Specs:
Windows 7
Amd 5200+ x2
2gB ram
HD4870
Theatron Agrippa Soundcard
Coaxial spdif to reciever.

Average cpu-load while playing: ~40%