I've only tested this on an Acer Aspire One D255, but this was an issue with a recent 11.1-STABLE snapshot and is still true with 11.2-BETA1. The installation from the memstick image went fine until it was complete and I got back to the menu which offers the option to reboot into the newly installed system, but the system becomes unresponsive so that it is impossible to highlight or activate any option. CTRL-ALT-DEL will still reboot the system.
Can you hit [ctrl]+t when you see this behavior? I have seen a sendmail process get stuck looking up the hostname of the machine being installed, but not entirely reproducible.
I apologize for the delay. I didn't have time to get around to any testing until the weekend.I can try 11.2-BETA1 again if you would like more info on it, but I tried out the 11.2-BETA2 today, and I did not have the issue with the installer with BETA2.
I know it's been a long time. I was tempted to close this, but I've encountered this a few times with newer versions. Just today I installed 12.2-RELEASE on a machine. It seemed stuck as I was finishing installation. I hit ctrl-t and, just as you said, it displayed something about send mail. I waited about a minute, and it proceeded further to allow me to reboot. I don't know if this would have happened on previous occurrences. But without any output by default, it at least seems to be frozen. So in any case, it still seems to be an issue that occurs seemingly randomly.