Headsets with USB connectors cause WebEx to crash on some Macintosh systems. If you experience this problem, switch to a headset with a 3.5 mm plug. These are available from the IT Services Help Desk, Room 330, x4400, firstname.lastname@example.org. Several styles of headsets are available including Apple Earpods (the headset that comes with an iPhone), and headsets with one or two earpieces.
Use these instructions to configure the headset.