I nothing helps, please provide some additional information such as your IT2006 version, some information about your mmc card (its size, filesystem type, general directories layout), as mplayer gui scans mmc card for video files, it may have some problems on your device at this step. Also it is interesting whether you are using swap or not. With more details it will be easier to figure out what happens and make MPlayer work on your device.
I nothing helps, please provide some additional information
You can run mplayer from XTerminal by providing url in its command line.