I've had that problem with MOV, AVI, and WMV files. I've heard that VideoEgg doesn't work too well with Windows setups a lot of times.
I upload my videos to petfinder.com.
The reason that I can put videos on Dogster is if my mistress uses her dad's computer, which is Windows but can handle VideoEgg.
P.S. Both my mistress's computer and her dad's computers are Xp.