Hi
We're trying to address the issue, but it's caused by Paypals horrible new security filters - and our sites have been involuntarily made a part of them. It's been causing problems for us, and we're trying to resolve this with Paypal but they haven't been of much help yet unfortunately aside from assuring us that the issue is with their filters and not our installation (which isnt much help) I really apologize about the issue - right now some of our customers affected by this are getting their payments through after a couple of attempts or by using IE and FF instead of chrome. I wish I could be of more help. We're trying to resolve this to the best of our ability, but unfortunately our control over the problem is minimal at the moment.
Thank you