I'm still working on this, but very sporadically (it's not my computer and I don't get to see it often).
Latest attempt is to install gnash but that (so far) hasn't worked either.
Bear in mind this is a problem in FF and in Opera so it's likely an OS problem (I've gone over everything I can find in that). Next phase will probably be an upgrade to 11.04 or 12.04.
A possible pointer to its problem is that the Plug-In check (for out-of-date plug-ins) returns a page showing ONLY an error.
In passing, following up information on the adobe site, it appears they are dropping linux platforms. The current version of Flash will be maintained for bugs but that's it. Which will hopefully allow gnash to catch up (hadn't heard of it until this debacle).
Adobe is also dropping a variety of mobile platforms from its support.
Shame. It has always been such an exploitable app. :)