I had Firefox working with the debug flash player that I downloaded from Adobe Flash Player Support Center following the instructions on http://ubuntuforums.org/showthread.php?t=1300563. However, today, an automatic update came into my Ubuntu 11.10, which upgraded the flash player to 22.214.171.124 (a non-debug version).
When I copied the debug flash player again per instructions in the ubuntuforms link, flash does not work anymore.
I guess that the problem might be related to this bug: https://bugs.launchpad.net/ubuntu/+source/flashplugin-nonfree/+bug/870835
If they are now using the 64-bit flash plugin, it would make sense that the 32-bit debug flash player (There is no 64-bit debug flash player for the moment) does not work.
Is there anybody who knows how to work around this so I get the i386 plugin back with the nspluginwrapper?