Problem with login.php

[lindendesign]

Hi there.

 

I seem to have a problem with the customer login part of the store.

 

If I access it in a secure url, such as trying to submit a review, or returning from the paypal express payment bit, when the username and password is entered and sign in is pressed, it just reloads the same screen.

 

Any ideas why this is happening?

 

Thanks,

 

Craig