SharePoint Datasheet Error: An Error 0x80070057 Occurred. No further information was provided

In the People picker field in SharePoint 2010 Datasheet view, on entering new values, I got this error message: An Error 0x80070057 Occurred. No further information was provided.

Moreover, the People picker field drop-down was empty!

Fix:

1. Open your list in SharePoint designer
2. Edit list columns >> Make some dummy modification to the “Person or Group” column which is causing the problem.
3. Hit the save button in SharePoint Designer once done.