I play a lot of online Flash games in my brower, and I updated to FF 18 as soon as it became available. Followed by Shockwave Flash 11.5 r502 on the same day. 11.5.502.106 to be precise. The first thing I noticed was extreme lag in the games, as they slowed right down.
Closing FF and restarting helped a little, but only for a while as the lag then resumed.
I've since reverted to FIrefox 17.0.1, and Flash works with that just fine.
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