server install not possible due to infinitely repeating asterisks

I just downloaded the latest Precise Pangolin amd64 server iso nightly build (March 15, 2012) and tried to install it. The install works well initially—I get through the keyboard selection at boot time, and am able to tell it to install ubuntu. However, when the install script starts asking questions that require answers to be typed (setting the machine name), chaos ensues: the UI behaves as if I am holding down the asterisk key continuously. I can type other keys, and those appear as well, but the asterisk key autorepeats continuously, so it's impossible to actually enter any data (e.g., username).

This is happening on an HP Proliant with a USB keyboard; removing the keyboard does not stop the autorepeating. Additional info: I'm booting off of a USB key (the Proliant BIOS seems okay with this). I never hit the asterisk key during install, so this isn't a lost key release event.