help with 404 error: can't create account

[divinelighting]

Hello,
Customer can't create a new account. After customer information entered, returns 'page not found.' (only for center column)

In address bar it says http://xxx/index.php?main_page=create_account

Have tried enable_error_logging but with no errors.
Have tried enable/disable ssl.

Any ideas or other debugging tools I should try?

Thanks!

[divinelighting]

Anyone have any ideas on this?

Thanks!