Yup, Annette put in a routine to 'force' avatars to the required 100 x 100 size. I'm not sure if she's already been made aware of this side issue, but I'll direct her to this thread anyway. I'm sure it won't be a huge issue to fix.
ETA: Or maybe they've already been fixed? Some of them look odd to me, but definitely not pixellated or huge - I'm afraid I don't pay enough attention at the best of times to know if they're back to normal.
LabRat