Please help

I was adjusting the rights of a user and disabled ‘Read’. I logged myself out and tried to log in as that new user. After doing that I get the message: Forbidden You don’t have permission to access this resource.
When I try to relogin whit my admin account I get exactly the same message. So I locked myself out and can’t find a way to fix this problem. When I surf to the URL I now get that same message described above.
Does someone knows how I can fix this without bringing more damage to my wordpress? Is there a way to fix this via FTP?
Help is very appreciated!