Flip camcorder movies

I just installed the 3.2 aTV on my apple TV.
Uploaded few AVI movies using the WinSCP program on my PC and it works great.
When uploading the Flip camcorder AVI movies - using the WinSCP, I could only get on the ATV the video but no voice !!!
When uploading the same videos that were converted and compressed with the camcorder onboard software into WMV format, into the apple TV once again using the WinSCP program, I got on the ATV exactly the oposite: Voice but no video.

PLs advise.

Thanks

M