touchpad: multitouch stopped working

[David Zelinsky <dzpost@dedekind.net>]

Running wheezy on my laptop, the touchpad had been working, complete
with two-finger scrolling and middle-button emulation.  But at some
point in the past three weeks or so---possibly after a
dist-upgrade---all the multi-touch features stopped working.  Mouse
tracking and single (left) touch-to-click work, as does vertical edge
scrolling.  But two-finger touch (emulating middle click), and
two-finger scrolling do not work, even though synclient reports that
they're turned on.

I presume this is a problem with the synaptics driver, though that
package doesn't seem to have been upgraded recently as far as I can
tell.

Any syggestions?  I really miss the multitouch features.

-David