Roxio Easy CD Creator 5 Platinum

I have a CD-R/RW LG Model GCE-8481B and associated Software Roxio East CD Creator 5 Platinum. I also have a Philips DVD Video Player Model DVD625K through which I watch my creations. When I try to burn video clips only two clips out of a dozen are successfully burned and I can watch on my Philips player. The others cannot beburned and a warning says that they have to be "converted", I do not know how to convert them as they dont give details about this problem and how to solve it. I would like to know why only some of my videos I can burn but not others although they are all from the same source. Many thanks Regrads - Khushroo