The story:
Yesterday I reinstalled Windows 7 x64 and, as always, installed CoreAVC 2.0, Haali Media Splitter and MPC-HC (lastest build, svn 1503), everything x64. Today I went to check Kanon 1080p and the video was pretty slugish. Not knowing the reason behind that I deactivated CoreAVC. And then... all hell broke loose...

WTF is that?

I haven't touched anything, just plain and vanilla MPC-HC. Even like that the video is still sluggish. I tried several files (HD and SD) and so far all of them, except Clannad by Coalgirls which plays fine, have that odd effect.
I played with some settings and it's the same. Too tired now, I'm going to bed. If someone can explain that he/she wins a cookie

PS: I used the same programs and versions that I had before, and back then everything worked fine =/