I've had very very similar problems with my 1300a. After some testing I found out that other software (Pinnacle InstantCopy 8) interfered with the proper working of my device.
Once I uninstalled this program, everything worked fine once again.
If you want to test your system for software errors, without reinstalling it, you could make use of a Linux Live CD. At http://www.knoppix.net you can download such a disc for free. You can simply download it and boot from it. It'll give you a graphical Linux environment that's quite easy to use, even for total newbies. Start K3B (burning program) and test the NEC from there. If that works all right, we know we have a software problem...
ps I moved this to our NEC forum