Those are the questions we have to ensure that people registering for the site are real and not bots, I can't think of any reason why you would be asked them before sending a pm.
My first instinct is that your phone logs you out, or at least appears to, so it assumes you have no account when you're trying to send the messages.
If you can could you send me details of what phone, browser etc you're using and I can have a look see if it's just you or if others have similar problems.
I would say PM me, but that may be difficult.
My email is aegis@ the web address of the site.
Cheers,
Aegis