All of a sudden the touchpad on my Dell D620 stopped working. After googling for an answer I came across a post on LinuxQuestions.org pointing to the solution.
To sum up, browse to Control Center > Sessions and deselect Touchpad from the Startup Programs tab. After restarting your session you'll be able to use the touchpad once again.
Note that the KDE desktop enviornment on OpenSUSE is unaffected by this bug, it only affects GNOME.
Props to LinuxQuestion.org user swampdog20002 having posed the question and posting updates on how he was solving the problem. That's the opensource spirit!