[PROBLEM] Can't play most of my videos

[Puntoboy]

1. First of all, we need to know what version of XBian you running on your Raspberry Pi
XBMC 12.0-RC1 Git:20121212-afbae11 XBian version 1.0a4

2. Is your system Overclocked the other way than XBian default or Turbo mode enabled ? If yes, please provide your OC settings
No.

3. What is your power supply power rating. This helps to eliminate the power related issues in process of troubleshooting
Power from USB port on TV

4. Do you have any device connected to USB ports of RPi ? This only applies to direct connection, without external self powered USB Hub
Logitech DiNovo Mini Keyboard wireless receiver

5. How is your RPi connected to the network ? LAN or wireless
LAN connected to a Gigabit switch

6. What SD Card you using ? Model, size. All possible information
Transcend 4GB SDHC

7. Provide the appropriate log file
http://pastebin.com/MuNVWSvC

The problem I am having with my setup is that most of my MKV files will not play in some way or another. I think I've only found one that plays. Some play the audio but the screen is black, some of them the counter comes up but the screen still shows the movie list.

So far I've found that any AVI or standard MPEG2 files appear to play OK.

Any ideas?