Mac Safari issue with checkout

a customer reports she can't checkout with Mac Safari as there is no visible Next button on the page. I can't replicate the problem and don't have a Mac. Windows Safari works fine.
What could be the issue?
the site is www.safka.co.nz

We don't have mac too, I don't really know why this happen.
Maybe a template issue, a property badly interpreted by mac safari.

Can she send a screenshot to you ?
Are you sure that she register correctly before trying to go to the next step ?