Have you successfully printed to tape before? Your symptoms sound like inadequate computer issues, though your hardware description sounds good. Is it the printed video on the tape that is blocky & disappears or just the preview when you start the print? Try printing some video to tape and play back the tape to see if it's OK. What you see isn't always what you get. Always check the cable first. Try defragmenting your hard drive. Also try closing backround applications using Ctrl+Alt+Delete. Don't close Explorere or Systray. You might want to run a virus scan too, as something could be eating CPU cycles without showing up. Be sure to check the cable, too. If you're using a Firewire card, go to Hardware Manager (right click My Computer, click Properties) and make sure there are no yellow triangles, especially with the 1394 Device (usually at the top of the list). In the BIOS, make sure you haven't disabled the RAM test at start up. Many of us do that to improve boot times, but if you have a bad memory module, it might only show up in RAM intensive operations. See if your BIOS has a CPU temperature readout. If it is running extremely hot, some mobos clock back the processor, or sometimes the processor can get finicky before it fails outright.

Good luck.