BMW X5 4,6IS -03
MKIV with version 4-1/12 (V20.1)

I downloaded the V27 file (mounted it with MagicDisc, burnt it with Roxio CD creator, lowest speed, on a Imation CD-R). The burnt copy works fine on my computer.

Tried the upgrade according to the instructions I collected after reading 30+ replies on this forum thread. .

After I inserted the disk the screen displayed some text about loading disc. It did not display any upgrade information text or question. The screen went blank. I left it running for 20+ min. Every now and then the screen "blinked" a little (but no information on it) and I can hear the CD in the DVD reader at the back spinning/reading the disk every now and then. After 20min I gave up. Took out the CD and inserted the map CD again. However, the screen remains blank (radio is working but no info on screen). Tried to turn off the power and back on again a little later. Still no information on screen.
Did I crash the old installation?
Is it possible to upgrade straight from V20.1 to V27 as I tried?
Any ideas how to solve it?

Thanks!