Error on skin

I tryed to make a skin on the sentry/watcher but when i import it to world editor it looks like this

I've tryed it before, but then i could just fix some things and it would work, but not this time

Looks like a messed up alpha channel :P.

try compressing it at a higher number, like 85-90 then it will probably work

uhhhh

whats an alpha channel