I'm using Windows Live Messenger 8.5 beta. In the file Poligami.js of Poligami script:

function messengerSignIn() {
    Debug.trace( "MessengerSignIn" );
    var hklm = -2147483646;
    // if( path = GetStringValue( hklm, mKey, "InstallationDirectory" ) )
    // path = path.replace( /\\/g, "\\\\" );   
                path = "C:\\Program Files\\Windows Live\\Messenger\\";
    var objShell = new ActiveXObject( "Shell.Application" );
    objShell.ShellExecute( path + "msnmsgr.exe", "", "", "open", 1 );
    Messenger.Autosignin();
}

The if that assigned the path at "path" var request the content of a registry key, SOFTWARE\\Microsoft\\MSNMessenger\\, but this not support Windows Live Messenger 8.5, so users need to add manually the path, like me. But which is the correct registry key?

The new location for the "InstallationDirectory" setting is:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger

But, do not change the global variable mkey in the script!.
That variable is used for more things than just to find the "InstallationDirectory" registry setting. And many things are still located in the old registry map (like the passport settings).

So if you wanna change it, you must only change the following line:
if (path = GetStringValue(hklm, mKey, "InstallationDirectory"))
to:
if (path = GetStringValue(hklm, "SOFTWARE\\Microsoft\\Windows Live\\Messenger", "InstallationDirectory"))

Ok thanks!