Not sure if this has been posted but I have a floating header bar and Sharebar didn't see that (most likely my own css), if you have a similar problem then open sharebar.js and on line 43 change:
jQuery(sharebar).css('top',((p+10)>start) ? '10px' : '');
jQuery(sharebar).css('top',((p+10)>start) ? 'XXpx' : '');
XXpx is your custom value. So if you want the bar to float an extra 20px from the top change the value to 30px.