The error could be related to the lack of supported codecs or due to the wrong settings used in the application. The first thing to do is to check what codecs you have installed. Go to the application, access the Settings menu and under Video look for the used Codecs. If there are only the standard ones that came with Windows then install CCCP. Restart the software and choose FFMPEG. After this procedure, load a file and it should work. There is no need to configure the codecs, unless you know what you're doing.