There is an issue with the latest version, 2.36.13032, of WebEx Productivity Tools for Mac OS when logging using Single Sign-On (SSO). (Mac OS:OS X Mountain Lion v10.8.5, OS X Mavericks v10.9.5, OS X Yosemite v10.10 to v10.10.3.)
Cisco is aware and working on the issue (#HD0008530187).
As a workaround, impacted users need to use their website, listed below, for scheduling.
Affected sites:
https://dukemed.webex.com
https://dukeuniversity.webex.com