First off, you have not wasted any money. You have thirty days to return it, if you really want to -- though I hope you'll give it a chance as we believe we may have solved the problem you are having -- and we stand by that guarantee.
As to our support staff not getting back to you, it's probably because they were dealing with someone else, not that they were ignoring you. Also, (and I don't know that you did this) very often people speak their phone numbers so quickly that they end up garbled, and our support staff tries to call them back but is unable to decipher the number.
In any case, the division by zero error is something that has cropped up recently in certain, but not most, nVidia graphic card drivers, and we've been working on tracking down what is causing it, and trying to create a workaround for what appears to be a graphics card driver bug.
We believe we have a fix and we will make it available tomorrow (PST) after we do a bit more testing.
I sincerely hope you'll give us another chance to win you over, and I'll talk to our support department tomorrow to see what may have happened.