It hasn't been a good uptime week for payment gateways. While Paypal struggles with internal technical issues, Canadian payment processing service PSIGate is experiencing extended outages for the second time in less than a week. The downtime at Paypal and PSIGate is the latest in a series of recent outages for services that allow web merchants to accept credit cards, following outages at Worldpay and Authorize.net.

The problems at Worldpay and Authorize.net have been attributed to distributed denial of service (DDoS) attacks. A series of DDoS attacks in April targeted online payment processing firms Authorize-IT and 2Checkout. Both those attacks were later attributed to extortion schemes in which attackers threatened to knock the firms' web sites offline.

PSIGate has made no public comment as yet about its performance problems.