When you sign up you receive one email stating your sign up has been processed, you should also later receive another email stating the Hosting account has been created, your site may not have been created yet, it may still be in queue.
We had sign ups disabled for server upgrades, in those days that signups were offline they were queued, i think there was 2-3 days of sign ups queued, so it may be a few more days before they all get created, if you received both emails though, please let me know, as your account may not have created correctly.
Thinking about it - I already had the domain name when I signed up to X10 hosting so perhaps I need to transfer the hosting to you first - do you think that could be it?
It doesn't look like your hosting account was confirmed, if it wasn't confirmed in a short period of time it may have been removed from the queue. You can try to re-request it again by going here: http://x10hosting.com/hosting/resendconfirmation
If it won't resend it you'll have to sign-up for hosting again.