The problem is that your Computer is not allowing your to write fast enough when you get the error message "Write command failed on device X:X:X Bad Medium Detected". This error means that the data is not getting to the drive fast enough. Using USB 1.1 uses alot of resources in the computer to transfer data to the USB drive, so you may not beable to get the 4x write speed. Make sure that you are using Version 2.314 and that under the Drives menu, you have a check next to "Enable Burn Proof". This will allow the drive to being more forgiving, by turning the laser on and off as it runs out of data. The other thing you could do to get the full speed of the drive is purchase a USB 2.0 card to go in the computer. You can purchase one from
www.orangemicro.com.
I personally bought the Plextor PS-88TU drive and Orange Mciro's USB 2.0 PCMCIA card for my laptop, and it works great giving perfect results everytime at 8x.