contact info is missing or invalid

I've been trying to book a flight, but every time when I click on purchase now, it starts loading, and after a while it comes up with an error message saying: contact info is missing or invalid and boots me back to the start.
My contact info is correct. What shall I do? Has anyone else had the same problem?

Thank you

try google chrome.. the later updates for I.E have been problematic for me.
Hope it helps.

I am using Google Chrome!
The problem happens with all browsers!!!!

I had the same problem, then found the solution... On the payment page, there is a field before your name for title, e.g. Mr, Mrs, Miss, etc. This field defaults to "Title". If you do not select a value and it's very easy to miss it. No error message will appear to tell you that you have not chosen a value for the Title field. When you progress with payment, you get the "Contact info is missing or invalid" message. Once I had seen this, I chose a title, and the website processed my order successfully.