A botched upgrade at UK payment processing firm Protx left thousands of online merchants unable to take payments earlier this week.

An update applied in the early hours of Tuesday morning is being blamed for problems in processing payments over two periods on Wednesday lasting a total of about 90 minutes. Protx apologised for any inconvenience caused by the outage, which has now been resolved. Its engineers are working to identify the root cause of the problem and take steps to prevent a reoccurance.

"Unfortunately, our payment service was unavailable during two periods today (12:25 and 13.11 and the second between 13.57 and 14.37) during which time transactions timed out and were not processed," said Simon Black, Protx MD, in a statement issued in response to enquiries from El Reg.

"All systems are now running as normal. It is likely that today's [Wednesday] outage occurred due to an upgrade performed yesterday [Tuesday] at 6am. The upgrade took place following extensive testing, but it was only during peak hours on our live environment that this problem came to light."

It's not the first time an upgrade at Protx has resulted in an outage. The firm experienced similar problems in August 2007. That time Reg readers reported being unable to reach the firm by either phone or email to resolve the problem.

This time around Protx seems to have done a much better job of informing customers and keeping clients aware of developments via its service monitor page.

Nonetheless, the incident left Reg reader and Protx client Mark less than impressed. "All day authorisations have been failing - their status page says things are back up and running but our website is still down," he said in an email sent during the time of the second outage.

Users posting to a thread on Protx's support forum also aired their gripes about the SNAFU.

Protx, a Sage subsidiary that's one of the largest payment services in the UK, processes credit and debit card payments for more than 10,000 online and mail order businesses. ®