"You can't edit this page now because you are already editing it on another
computer. Click here to make this page editable."

This error message appears after I have made an edit then published a page or
create and publish a new page. When I refresh the page the error goes away.

If I follow the instructions to "make page editable" it just says "Access
Denied. The file may not exisit, or there could be a permission problem." I
clikc OK the page refreshsed and the error is gone.

I am the only user/Admin who is connected to the site from one machine.