I have seen a lot of sites using the ShareThis button (including a few of mine) where the button in Safari was getting cut off (clipped) at the bottom. If this is happening to you – there is a quickfix. Add this line of CSS to your stylesheet and your button will no longer be cut off.
.stbutton {display:block;height:16px;}

Thank You!
Glad I could help!
yes. truly. thank you. was going a little nuts on that one.