If you are not a regular follower of the Sidux
forums, you might get bitten by this one.
The problem apparently is not related to the current Sid upgrade of Hal, but that upgrade exposes a bug in xserver-xorg-input-evdev
Before upgrading Hal ...
# aptitude remove xserver-xorg-input-evdev
... That will take xserver-xorg-input-all with it, but leave xserver-xorg-input-kbd and xserver-xorg-input-mouse (and presumably any other individual active input devices) in place.
xserver-xorg-input-evdev evidently provides some kind of priority handling for the various input devices, but removing it has not had any obvious negative effect on my system.