Flash player 10 non free (or free indeed)

[Eric]

I'm having some troubles here.

As all Ubuntu user (I guess) I'm navigating with Firefox 3, all sites
tells me I don't have any Flash player installed. However any time I
want to install Flash player 10 plugin from Adobe on Ubuntu gestor tells
me I have a posterior version already installed...

Any option I tried from gestor failed due to the "posterior version" yet
installed (I installed gnash too).
But in the end... nothing work.

If you have any solution, thanks to tell me.

Eric Giovannoni
Monterrey, N.L., México.