I have finally acquired Internet to my house and, since I again have access to the Intarweb and fabulous forums such as these, I felt that it was time to put Linux back on my home PC for all but gaming. Quickly, Ubuntu 9.10 x64 came down the line and a little while later, I have a fully installed Ubuntu system. On top of the vanilla install, I've added the nVidia proprietary drivers (using the U.I. to install them for the first time ever... and being much surprised by the fact that that WORKED!)

Now I have some hardware:
Intel E6850 Core 2 Duo
nVidia GeForce GTX 275
Some (4GB) generic RAM
Lots (all added up, over 1 TB) of hard-drives.
Onboard sounds (Intel HD Audio)

And some Software:
Ubuntu 9.10 Karmic, x86_64.
nVidia Proprietary Drivers
LIRC (for my Windows Media Centre (green button) remote)
XBMC (off the PPA)

... and all is well.

But all is NOT well. Despite the fact that I've achieved this without hacking a SINGLE LINE OF CONFIG FILES or compiling a single program from source, I do have a problem: I have some serious video tearing in XBMC when playing video.

I have enabled "Vertical blank sync" under System -> System -> Video (inside XBMC) but this hasn't changed anything. (It HAS given XBMC a tendency to hang, however.)

Specifically, I noticed this when watching h.264 video from a Matroska container.

How should I start tackling this problem? I've fallen in love with XBMC already (out-the-box support for my remote and such a customisable U.I.) and don't want to lose it to some silly tearing problem.