I opened Synaptic, searched for "flash", saw that Adobe Flash v10 was not installed (huh?!?!), installed it and things seem to be OK now. .... but why was I getting the error message if Flash wasn't installed?
I just started getting that message on THIS page as well as others, only in the last 3 days though. They really need to release a patch to fix this soon its really slowing down firefox. i have the flash 10 installed from the package manager BTW was installed by default.