ubub1: device problem (IOERROR), disabling port 2

[n dhert]

On a Dell Optiplex210L (no PS/2 connectors) I installed Freebsd 7.2 a few
weeks ago.
All OK.
Then swapped the disk for a empty larger one, wanted to install freebsd from
the
7.2-RELEASE-amd643.dvd1.iso (as I did before).
In BIOS, and at FreeFSD Welcome screen keyboard still works, but later
during kernel initialization, I see:
usb1: host controller halted
uhub1: device problem (IOERROR), disabling port 2
and I can't use keyboard and mouse anymore, hence can't install.

Swapped the disk again for the original one.
Now I have the same problem when booting into FreeBSD, which booted a few
weeks ago ...

What is going onand how to solve it ?
(No options in the BIOS for USB legacy support)