[aznjackass343]

It's because the compression has probably been removed while converting, and extra junk has been added.

You could use some other converter if this is not the problem, like Videora Ipod Converter.

Also, the installers for iPod Linux on Nano's are not supported, so don't come to Unknowing crying, you are doing this at your own risk

It should work in theory, but if it doesn't, do a restore in Itunes.