The cpu usage for the "fontd" process was at 50% when I started the Flash Player.
This happened to me a while back and I fixed it by going into the Font Book app and turning off all but the required apps that were locked. (Noticeable by the lock icon on the bottom of the right hand corner). I heard this issue effected only Snow Leopard users but I am currently running Lion.
Mac OS X (10.7.2)