The problem only occurs when trying to change the focus from the blur event of the last enabled field on the form. (No buttons after it or anything else.) When you tab out of the last enabled field on the form, the focus goes to the address bar. Even though you issue the command to change the focus back to the field, the cursor gets stuck in address bar.
I was able to create a workaround by creating a text field with width 0 as the last field on the form. Since this field has 0 width, it isn't visible and doesn't affect the functionality of the form. With this field in place, tabbing from the last field on the form would go to the 0-width text field instead of the address bar, and now the blur event is able to set the focus back to the field that fired the blur event.