You are receiving an Unable to save given Data error when creating a new task.
The error details are as follows:
Error Number : 42005
Error Message : 42005 : UNABLE TO SAVE GIVEN DATA
Error Source : ECONTACTMANAGER.TOCONTACTMANAGER
Error Method : TBOCONTACTMANAGER.SAVE
Further investigation shows that it is a database issue:
Arithmetic overflow error converting IDENTITY to data type int.
The issue is related to the new identity feature from SQL Server 2012 which is designed to boost the performance of high-end machines.
To solve this issue, please follow the Steps section from the Arithmetic overflow error on IDENTITY column Tasks.task_id article.
The steps in the related article should have helped and allowed you to save new tasks. If the problem is still manifesting, please contact support.