Liteon-lh20a1 Speed Problems

i have just burnt a disc using pioneer108 usb2 to liteon lh20a1 which is set to master.i am burning on the fly andit took 10 mins 30 secs to burn using ritek go5 dvd-r media.it started to burnok thenfor some reason the speed dropped to 6x for most of the burn.
i have used nero 8 and just used dvd copywith same results,can anyone help please
ive had some problems lately as i also have a pioneer 112d drive which i have disconnected as i am waiting for longer ide cable so i can use internal drives

Burning on the fly using an USB connected drive is not a very good idea.

The USB connection is a huge bottleneck, mostly if the source disc has some difficulties like minor scratches or dust that can slow the read process.

The best thing is to copy first the source disc on hard disc, and then burn from the HDD.

What happened then is normal because the USB connection is too slow to guarantee a fast enough data flux to the burner.