D’oh. Thanks sociable. I should have checked my own css.
Having the same issue with my icons since 3.5.1 (now upgraded to 3.5.2). I didn’t change the icon size or try anything funny. Sample here:
jetpack powered by water/
With the last upgrade, I fixed it by modifying sociable.php and changing the icon offsets slightly to get the full icon to display. Don’t feel like doing that again.
Oh, and it happens in both Firefox and Opera.