When trying to save a specific Incident, the error 'Arithmetic overflow error converting numeric to data type numeric. This statement has been terminated.' pops up and will not allow the record to be saved. It does not happen for all Incidents.
This issue is generally due to an overflow of the Cost field. By default, the Cost field is of the type decimal(6,2), so it supports a maximum value of 9999.99.
If you open the Task(s) attached to the affected Incident, usually you'll find that the Cost of the time logged totals more than $10,000, causing the overflow when the Incident tries to roll up the Cost on resolution. You can either expand the Cost field to decimal(10,2) in configuration, or edit the Actual Effort field on the Tasks (often the high number is due to a typo or mis-keyed entry).