I finally got t'he solution
The problem was t'he New lion feature called "multiuser vnc".
When you acces from "not Lion" device you must
choose The same id user and password that you have
Active in that moment, on The identificacion screen. If that screen don't
Appear must be because you have had one wrong acces before.
In that case you must uncheck "screen sharing" and érase "vnc pass".
Then restart The Mac. After this you check that 2 options. You see that The
System ask permission and you must put The user password.
Then you can try The vnc correctly. You must be sure Of putting The active user when The vnc client ask you.
I have got acces with SL Mac, iPad (with cloudconnect and vnc lite) and with an iPhone. In all
Cases inside lan and on remote, with 3G.
The especial case is that The "vnc password" don't make any función. None Of The
Programa Asks me. But finally i think that is better that it exist ( because when you
Change or Check that Pass Lion makes changes inside The System).
I hope all if this goes OK for you