While the underlying cause of this behavior is not currently know, to resolve the issue, perform the following steps:
1. Log in to the Web client as the user experiencing the problem.
2. Select My Preference.
3. Click the Subject drop-down arrow and select Telephone.
4. It is not necessary to adjust any of the selected columns. Click the Save button.
5. Click the Exceptions tab and then the Telephone tab; the error message should no longer appear.