My site is up and running, but lately I noticed that once the user log-in they get a 404

"
The requested URL /redred was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

When they hit the back button they are already logged-in. I also noticed that once log-in and you want to view your profile. You get the same 404 page.