turns out that turning off javascript was preventing flashplayer from being invoked.
libflashplayer is (from adobe) libflashplayer-10.0.22.87.linux-x86_64.so.tar.gz
2009-02-02 23:03 libflashplayer.so
which had been (also) working fine under F10.
(gdb) backtrace #0 0x0000000000000000 in ?? () #1 0x00007fffdf88d59a in ?? () from /usr/local/adobe/libflashplayer.so #2 0x00007fffdf9d5a19 in ?? () from /usr/local/adobe/libflashplayer.so #3 0x00007fffdfba504c in ?? () from /usr/local/adobe/libflashplayer.so #4 0x00007fffdf88f3be in ?? () from /usr/local/adobe/libflashplayer.so #5 0x00007fffdf8863d9 in ?? () from /usr/local/adobe/libflashplayer.so #6 0x00007fffdf87b9c8 in ?? () from /usr/local/adobe/libflashplayer.so #7 0x00007fffdf87d398 in ?? () from /usr/local/adobe/libflashplayer.so #8 0x00007ffff759788c in ?? () from /usr/local/firefox2/libxul.so #9 0x00007ffff75a3207 in ?? () from /usr/local/firefox2/libxul.so #10 0x00007ffff759be23 in ?? () from /usr/local/firefox2/libxul.so #11 0x00007ffff75a5d35 in ?? () from /usr/local/firefox2/libxul.so #12 0x00007ffff70e6517 in ?? () from /usr/local/firefox2/libxul.so #13 0x00007ffff70e96e0 in ?? () from /usr/local/firefox2/libxul.so #14 0x00007ffff71f83e0 in ?? () from /usr/local/firefox2/libxul.so #15 0x00007ffff71f87d7 in ?? () from /usr/local/firefox2/libxul.so #16 0x00007ffff772212a in ?? () from /usr/local/firefox2/libxul.so #17 0x00007ffff76f6545 in ?? () from /usr/local/firefox2/libxul.so #18 0x00007ffff76624f3 in ?? () from /usr/local/firefox2/libxul.so #19 0x00007ffff753c0a3 in ?? () from /usr/local/firefox2/libxul.so #20 0x00007ffff6f1644f in XRE_main () from /usr/local/firefox2/libxul.so #21 0x0000000000401b10 in close () #22 0x000000341481ea2d in __libc_start_main () from /lib64/libc.so.6 #23 0x0000000000401909 in close () #24 0x00007fffffffe3f8 in ?? () #25 0x000000000000001c in ?? () #26 0x0000000000000004 in ?? () #27 0x00007fffffffe781 in ?? () #28 0x0000000000000000 in ?? () (gdb)