Problem: Getting Error.
In my customer's case he was getting this error when he was in a task and had hit the complete action.
Cause: Address lookup is enabled on an object that shouldn't be. These are settings for an old feature that we no longer have in Service Desk. The old .dll was called CapCIAsm and is no longer shipped with Service Desk(7.6 and future releases).
1. Open Object Designer and find the Activity Task Object that you were using when the error occurred. In my customers case they were using the Human Resources so we went to Object Designer > Human Resources > Activity Task.
2. Click on Address1 attribute.
3. This attribute has a String SubDataType of AddressElement1. Change that to 'None'.
4. Now click on the PostCode attribute and set the String SubDataType 'AddressPostCode' to 'None'.
5. Save and test.
This happens in 7.5 SP1 and below. This has been fixed in 7.6 Out of the box database.