All skins error out even if they're 64x64 or 64x32

For some reason when I try to create a new skin and import a skin image it errors out, saying;

"Skin images must be 64x64 or 64x32 pixel PNG files."

even though the skins I import ARE 64x64 and 64x32.

This bug is so weird. This has to be fixed. I'm currently playing in my laptop because my main PC is not available.