Customer Login Page - 404 Error

[bowsbride]

Hi

I've had my site running for a while (has been working) and I've just realised that when customers try and reach the login page, they get the 'No Page Found' 404 error (from my site). I've checked the files and I'm sure they are all there? I have even tried the default template and that is giving me the same error. What files does the login page refer to?

You can see the error on the following link
http://www.bowsbride.co.uk/index.php?main_page=login

Also, my admin login page isn't displaying properly as well. Could this be related?
http://www.bowsbride.co.uk/admin


Look forward to your help

Toby