Obsessed With Turtles
Join Date: Jan 2003
Location: Land of Procrastination (MN)
it is 80x80... BUT if the file size is larger than the limit it will also get rejected. As Becki said make sure custom avatar is checked.
One other thing you could try is saving it in a different format. (if you have been saving it as a bmp try saving it as a jpg or gif instead.)