I had problems using a debit card for livenation.com transactions before, but my order (for a different artist) went right through once I switched to using my credit card. Something with the computer system perhaps.
This time around I had to keep re-trying for a bit over 25 minutes, but it eventually worked. This stuff happens with all ticket sales. But compared to other fan sites, this site has way more tickets available for presale on a regular basis, and at far better prices.
Sorry it didn't work out for you though. I've been shut out here before. It's not fun, but it's not personal either.