Is your photoshop cs5 up to date.
Go to Help>Updates in photoshop cs5 and see.
You need at least photoshop cs5 12.01 on 10.8 for the droplets to work right.
(the newest update is 12.04 for photoshop cs5)
http://helpx.adobe.com/photoshop/kb/droplets-dont-photoshop-cs5-cs4-1. html