Aren't you using Roxio's Toast? It should have come with the external burner (well at least in my case it did). The Lite version is really great for a Mac.
From what you say in your post, I figure that you are trying to use drag-and-drop in the Finder, then burn a CD using the Finder's own Burn function. Am I right?

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-