Why core 4 player for 5250 (nokia) is creating a problem?

Hi. I purchased nokia mobile 5250 and installed different applications. But core 4 player for 5250 is not working properly as it supports format MPEG, AVI, MP4 etc. When I play mkv file, core player does not respond and the screen is black. I tried to download core player from different sites but same result. Please tell me what is the problem? Any fault in mobile?
