They are working on moveing from server 2 server heres what they said
mtabeta.com difficulties - Monday 4 February 2008 (09:10)
We are currently in the process of switching servers for our mtabeta.com community system. This will be causing some downtime for the entire system, but we expect this to be fixed later on today.
Update 5/2/2008
For all of our new users trying to install the Multi Theft Auto: San Andreas Developer Preview 2 release: the installer relies on the above system, which is currently not online. A result of this is that the installer will fail to provide you with a serial which is needed to launch the application.
We kindly ask you to hold on a little longer for our next Developer Preview 3 release (containing an updated and working installer) - or the launch of our mtabeta.com community system at our new hosting facility, whichever comes first.
We apologize for any inconvenience.