A customer removed "comm_isalldayevent" field from the CommunicationSchedulingBox (Administration -> Customisation -> Communication -> Screens).

Now when they then went to create a new task they got the error:

An unexpected event has occurred: EAccessViolation: Access violation at address 1A6AC095 in module 'eware.dll'. Write of address 00000019

Work around / Resolution:

Restore the field "Comm_IsAllDayEvent" to CommunicationSchedulingBox.