Thanks to lowjoel, we have the answer to this mystery!
When running MC on a Windows 2008 Server (R2 or not) there is some IMPORTANT things to consider.
1. If you want MC to update Duration and Dimension on video content, you need to enable the feature "Desktop Experience" under Server Manager and features. MC obviously have some deeper connection to basic video playback component in this feature.
2. If you need sound, or the ability to play music and video on this server, you need to set the service "Windows Audio" to Automatic and start it. Without this, you'll never get sound in Windows. You also have the option now to run Null Audio Renderer as playback device in MC, so this might not be necessary to actually check if things play in MC.
3. If you use Remote Desktop to connect to the server, all sound devices will stop working on the local server. No matter what options you choose, or hack the registry. MS have just made RDP on 2008 server this way, and have no plans on fixing it. If you want to enable sound on the server and keep it that way, you'll either have to use another Remote desktop product like VNC, Team Viewer or similar, or you have to use local access only.
I hope this will help someone else as well. I guess there is more than me that uses 2008 server.