As Peter Hutterer explains it (http://who-t.blogspot.com/2010/11/how-to-ignore-configuration-errors.html), synaptics InputClass handler should `MatchDevicePath
"/dev/input/event*"' on Linux. Otherwise I experince the second variant of the problem he discusses.
Rather too terse, but I guess the package maintainers would get it.
This bug is a duplicate of bug 345981
*** This bug has been marked as a duplicate of bug 345981 ***