Gotta b 75x75 pixels or less
that isn't the problem. it's just not the problem. what is so hard to understand about "that is not the problem," it is never the problem
if you upload an avatar that is too wide or too tall it resizes it, it's always done that
the problem here is either:
a. the file size is too large, so compression is needed. not necessarily by reducing the resolution however that is an (ineffective) option
or b. the forum's just messing up again