Got any other dvd writers to try the verbatims out?
Your verbatim could be fakes. Did the packaging look like normal verbatim, did anything look weird with the disc. You can also look at the serial numbers on the discs. One is on the clear centre part of the hub, should begin with PAPA or PAP6 or something like that. The next part is on the recording part of the disc, in the dark purple spot. Should say something like ZD9575 etc.
Hard to say what the problem is at the moment.