nx surveys, how to get around the glitch?

I used to be able to charge with PayPal (like, 2 years ago) but then it simply stopped working due to PayPal's fault (high risk transaction or some crap like that). Then I started using PayByCash but that had an extra fee of $10 or so, so I didn't use it that much. Now, when the card function became available, I started using it and it worked fine, but after reaching the charge limit on my main account, I started getting that error:0 thing on ALL of my accounts.

Well, yeah, now I'm stuck to buying NX card codes from ebay (cheapest I've found is $6 extra fee).