I've just downloaded the latest nightly build of Ambient (1.43.0). After using the provided install script I rebooted and Ambient came back up. When I moved my mouse it was very jerky, and the mouse buttons were not responsive. I tried pressing RAMIGA-N to bring up a shell window, but nothing happened. I powered off and back on again, but the same thing happened.
Fortunately I backed up my Ambient drawer before carrying out the update so I booted from my MorphOS CD and replaced it with the previous version. Everything was ok again. I downloaded the previous nightly build and tried that, but the same thing happened.
I was going to try the latest stable release, but the file appears to be missing from ambient-desktop.com