Adobe flash player not working?

Hi all,
I have a late 2007 24" iMac, running Snow Leopard 10.6.8. I have flash player version 11.5.502.146 (the latest version) installed. But when I try to watch a flash-enabled video on the web, it says install flash player to view this (paraphrasing). The flash player shows in my System Preferences. I even deleted it and reinstalled it. But things are acting like I don't have it.
This started around the time Apple restricted Java a week or so ago.
Any ideas on what I should do to make it work again?
Thanks for any help/advice.
Edited to add:
This only happens with Safari. Firefox is fine for playing flash videos. I have Safari 5.1.7

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Fixed. I had "Enable plug-ins" unchecked in the Security tab of Safari preferences. D'oh.