Credit card orders are coming through as cancelled, even though DPS has taken the money and put it in our account
Please check the magebase_dps log under [siteroot]/var/log/ for any messages (first enable logging in your admin backend).
It's likely that you're getting a value mismatch for the order total. This can happen when you use shipping costs that have more than 2 non-zero decimal places. ie. 3.5692. There is a stringent check on payment return that verifies that the paid total matches the order total. The discrepancy comes from the order total being calculated at the full precision and the paid total being rounded to 2 decimals.