Player 10.1 beta 3 was released on February 23, 2010.
If you want to install the debugger version of this release on a 64 bits Linux box you have to install a current 64-bits non-debugger version first.
After that you can replace the installed
libflashplayer.so by a 32 bits debugger version of this file.
This also applies if you want to install the debugger version of the current release, see note2 below.
This is how i did it on 64bits Kubuntu 9.10: