I had the same problem, found the tutorial here:http://forums.linuxmint.com/viewtopic.php?f=208&t=117665&p=651427&hilit=panel+icons#p651427
To solve this, just go to Cinnamon
Settings (right click the panel) >> Panel >> check the two boxes:
"Use customized panel size (otherwise it's defined by the theme)"
to scale panel text and icons according to the panel heights"
This solved my problem without restarting Cinnamon
, though the tutorial said i have to restart cinnamon