On a 64-bit version of Ubuntu, you have a few choices when it comes to the Flash Player Plugin:

You can:
• Install the Flash Player 10 32-bit on your machine, but there is no point doing so as a new version of Flash Player 10 Linux 64-bit has been released.
• Install the Flash Player 10 Linux 64-bit. A good choice if you do not need the Flash player for debugging.
• If you are using the Flex Builder as a plugin in your Eclipse (Yes, you can, and it's free so far!), you can use the Flash Player 10 Linux 32-bit debugger on your Ubuntu 64

I've found many blog pages with sh scripts to install a 32-bit version of the Flash Player 10 (non-debugging), but none for the Flash Player 10 debugger 32-bit. In fact, I'm wondering why you need the sh in the first place, because when I replaced the 64-bit Flash Player plug-in from my .mozilla folder with the Flash Player Debugger 32-bit, it just worked right away! I didn't have to fool around with the getlibs or anything, and here I'll try to described the few steps it took to do it. First thing, Adobe wrote in its ten frequently asked question about Flash Player that it will not release a debugger version for 64-bit:

Is there a debugger version of the 64-bit Flash Player available?

We currently have no plans to release a debugger version. (See it here)

I'm not sure whether you need to install the 64-bit Linux Flash Player plug-in first (as it was installed on my laptop) or whether you can grab the 32-bit debugger version from a clean installation.

1. Go to the Adobe FP10 download page
2. Scroll down until you see Linux Debugger and Standalone Players for Flash Developers and download the file there: Download the Flash Player 10 Linux debugger and standalone players (TAR.GZ, 16.3 MB).
3. Open the terminal, and wherever you have placed the file, type:
   
   tar -zxvf flash_player_10_linux_dev.tar.gz
4. Once this is done, type the following:
   
   tar -zxvf flash_player_10_linux_dev/plugin/debugger/install_flash_player_10_linux.tar.gz

   The previous tar extracts two files of interest in the instal__flash_player_10_linux folder. The first one is the installation script. Unfortunately, you will notice that if you try to run it from the terminal, the installation will fail because of the 64-bit architecture. However, you can still copy the libflashplayer.so file into the mozilla plugins directory and enjoy the debugging features.

5. Place the libflashplayer.so in your mozilla plugins directory:
   
   cp install_flash_player_10_linux/libflashplayer.so ~/.mozilla/plugins
6. Open Mozilla Firefox, then click on Tools > Add-ons and you will see Shockwave Flash 10.0 r32. But in fact the version running now is the debugger.
7. In the terminal, type:
   
   rm -R flash_player_10_linux_dev
   
   and
   
   rm -R install_flash_player_10_linux
   
   to remove the installation folders.

If you are using the Flex Builder in Eclipse, you will be able to display the traces from your MXML/ActionScript from the Console panel:

Please post a comment here to let me know whether this has or hasn't been working for you!