Hi Paul,
I had a bit of a different problem with DIBS. The last part of my payment, the verification of my credit card, did not come thru though my bank could see I made the payment. So it is obvious the issue is at their site.
What helped me at the end is to use Safari instead of Firefox (I am on a Mac). This should not make any difference but it did. I informed Phase One about this.
If I recall correctly you can also pay via PayPal. I hope that will work out for you. And report your issue to Phase One anyway, they should now about it. And maybe can help you with another way of paying them (that was the advice my bank gave me) if PayPal does not work for you.
You can contact their Payment Department here:
https://www.phaseone.com/en/FooterMenu/Contact.aspxGood luck!
cheers,
Remko
Edited: corrected a typo.