A customer of mine is having trouble purchasing from my site. This is what they say:

After filling in all the account information as requested I click on the continue button. A small circle with a line goes round and round and nothing else happens. I've waited and waited but ended up having to cancel the order. I've tried several times over the course of a week but the same thing always happens.

They are using Google Chrome on Windows XP.

Any idea what could cause / fix this?

Thanks.