The cursor flashes rapidly, and when placed over an object the object flashes rapidly.

The cursor flashes rapidly, and when placed over an object the object flashes rapidly.

There is an invisible object corrupting the file. To remove the object, do a select all. Then, Shift-click on each of the visible objects. Now everything will appear unselected, but the cut command in the Edit menu will still be active. Either choose cut or hit the Delete key to remove the invisible object. Save the file, once the problem has been removed.