From within Preferences in a database in Lotus Notes the following error / dialog can appear: Your availability time range is invalid, please correct.
This dialog appears from within anywhere within Preferences - even if you are not editing availability information. This is due to Notes checking the validation for 'every field' after editing any field.
The error occurs when invalid time periods have been entered within Tools > Preferences > Calendar & To Do > Scheduling; see screenshot. Invalid periods usually involve a mixture of 24-hour and 12-hour times:
09:00 - 12:00, 13:00 - 17:30
09:00 - 12:00, 13:00 - 5PM
09:00 - 12:00, 13:00 - 05:00
09:00 - 12:00, 13:00 - 0:00
For an unknown reason Notes also checks the validation of fields where the checkbox has not been ticked, ensure these are checked too.