I don't know what the issue is with Zombaio and don't pretend to. However, it is a great idea to have multiple payment processors. The best ones are the ones you know already such as
http://www.segpay.com
http://www.ccbill.com
http://www.epoch.com
http://www.netbilling.com
etc
Stuff can happen with anyone for any reason. Even reliable processors and service providers can have issues once in a while. So what you may want to do is sign-up with several processors and if you experience any problems that may take longer to fix than you are comfortable waiting for, plug-in one of your other processors until everything is fixed.