Why am I receiving "... is not a number" (or "You must enter a value for the project field")?
This error usually comes from the browser auto-populating a field with a saved value that has been entered previously. If you look through the other tabs of the item you are creating, you could find the field. You should be able to delete the value as a saved value from the browser’s Tools or Options area.
If you don't want Firefox to remember what you've entered into form fields, you can turn off the auto form fill feature:
- Click the menu button in the top right corner and choose Options.
- Select the Privacy & Security in the left panel.
- In the drop-down menu for History, choose "Use custom settings for history."
- Remove the check mark under Forms and Autofill.
- Close the page; any changes you have made will automatically be saved.
You can also delete AutoComplete history on a PC for IE11 - see this link.