I had a problem installing the flash debugger v10, as a plugin to firefox, on my ubuntu system. The install script always keept asking me for the path to my mozilla browser and no matter what I put in there nothing worked.
I ended up searching for where the libflashplayer.so file is located on my machine and found that it was here
/usr/lib/flashplugin-nonfree/libflashplayer.so
So just copy the debugger to there
Here it is possible to verify what version of the player you have installed and whether its the debugger or not
http://kb2.adobe.com/cps/155/tn_15507.html