Ulead DVD Movie Factory 6 problem

For some reason when ever I try to add certain MPEG files to a new DVD Project the program all of a sudden closes down. There's nothing special or different about them that I can tell. Other MPEG files are accepted just fine but others cause the program to to shut down and I am unable to add them to my project, regardless whether I drag them over or use the program's search option and add them that way. Please help if anyone has experienced this and can explain what the hell is going on. Also, is there anyway I can have more than 3 files displayed one a single menu page? Thanks for any help.