I didn't realize this forum was for multible products.
I am using Magix Movie Edit Pro 14. Any mpg file I try to load for editing will not drop into the track. They also will not play in preview. The files are from various sources and play just fine with Windows Media Player and can be loaded into Windows Live Movie Maker for editing.
I bought this Magix product because I don't like the free Windows Movie Maker.
You really need to follow johnebaker's suggestion and post the information about the file using the tools he suggested. All mpeg files are not identical (and I am talking about how they are formatted, what codecs are used and on and on). So you may be able to open one but not another because of how it was formatted. If you download one of the tools that John suggested, have it analyze a file that you can't open, provide a screen shot of the analysis, it will be much easier to help you solve the problem you are having.