Which payment option did you try to use? Thanks to your suggestion the site is now full HTTPS. We don't get any of your payment details, all payments are handled by a third party payment processor. You can use whatever name/info you want to create the DirtyBin account, when you make a payment all the system does is associate the paid subscription with your DirtyBin user account. As far as the "SpeedBit" issue, I have never seen nor heard of it. There are a total of 3 ads on the site, none of which try to install software. It sounds like a malware/spyware issue on your computer.
As I suspected: "Go.Speedbit.com got on your computer after you have installed a freeware software (video recording/streaming, download-managers or PDF creators) that had bundled into their installation this browser hijacker."
Removal: http://malwaretips.com/blogs/go-speedbit-com-virus-removal/