Lacie Lightscribe Burner says I need 1.2GB capacity to burn??

I have a basic Mac Mini (no superdrive) so purchased a Lacie DVD burner with Lightscribe... I tried to burn using iDVD. I have read on this forum that they don't not allow burning from 3rd party devices, so that I understand, but I try to burn using Toast 6, (even tried an earlier Toast application) Once I put a couple of videos and couple of tracks (which is the only media files I have on there at the moment) and try to perform a "data" disc, and hit the red record button and so on, the desired speed is set at "best" although I have tried the "16x" speed and even the "1x" speed, and after I choose record, it says it cannot copy, That - 1.2GB of capacity is required (xxxxx no. of sectors) etc. Which is a bit weird seeing how I have approx 27GB free on the Mac Mini..

There's nothing really to free up or delete on the Mac as most of the installs are simply updates. Mayube it's a media problem with the DVD's themselves? Hopefully someone else can provide any info on this