I finally got flashplayer to work under opera in ubuntu.
I had it already working under firefox and all i did was follow "instructions set 2."
In your case i would put the libflashplayer.so file (that comes in your flash .tar.gz) in a directory (lets call it /usr/lib/opera/plugins, but it can be any directory) and then add this directory to opera's plugins paths like this:
"-> instructions set 1:"
open Opera
Ctrl-F12
click on "Advanced" tab
click "Content" (left side)
click "Plug-in Options..."
click "Change path..."
add the new directory (if "/usr/lib/opera/plugins" is not already there
"-> instructions set 2:"
Open Opera
Click on Tools-Preferences
Go To The Advanced Tab
Click on Downloads (left side)
find the one that says 'application/x-shockwave-flash'
Click Edit
At the bottom it says Use Plugin
select the one that says: 'Shockwave Flash - /usr/lib/flashplugin-installer/libflashplayer.so'
Click OK twice to exit out.
I had three selections under here, the other two said flashplayer alternative, or something to that effect. As soon as I clicked on the one above, it all started working. I tried it on Youtube. no problem
That worked for me!

Hope it does the trick in your system too
PS: sorry for the long post, but a newbie can't post links and i had to copy and paste here instructions from ubuntu forums