I'm assuming you are using a PC not a MAC; I own the same camera and it makes .avi files. I have used them in Sony Vegas and WMM. Check that you have the right Codecs. also try this free software Virtualdub
sony vegas has a free trial and is much easier to use than adobe in my opinion. I would just do this if you want simple editing.
Some people I know had the same problem and it has been different reasons that it happened; AC3's and codecs would be my first guess.