External device won't copy CDG

[wired2up]

Iv'e installed a Plextor DVD-708a in an external case and use the USB 2.0 to install and retrieve CDG's. On my desk top I uasually just copy from Nero using there Karaoke format and have no problems but when I try that from my laptop using the external Pextor all I get is the audio and no graphics, also on my desk top I'm using Pioneer 108's with no problem, I'm kind of surprised I'm having any problem with the plextor. Could this be a speed problem, I'm burning at 8 on the laptop the same speed I use on the desk top, also using the same media that works on the desk top Ritek Pro Series with printable top. Thanks again Bill