look at it!

Woa...

I believe the max size for avatars is 125x125, and your width is 135, so maybe that's why it's messed up.

Correct, it is too big.

The aspect ratio actually appears to be reversed.

if you cant fix it, dont remove it.
It looks rather good

Uh its a problem in the code where the width needs to be swapped with the height. It still won't look pretty but at least it'll appear in the same aspect ratio and prehaps readable.

what size shouold I make it?

Um.... anything that doesn't exceed the limits by having one or both dimensions over 125?

If you want to keep the aspect ratio and Tau is right that SEN is mixing up the width and height of your avatar, then 125 x 46 is the ratio you want.