Installation hanged (black screen on startup)

[Porcinet]

I tried to install Lion on my Mac Mini 2009. After downloading the i stallation file, I launched it (I also created a backup DVD beforehand). The first part of the installation took 3 minutes then it restarted the computer.
However, since then, my computer refuses to restart. The screen stays dark (although the computer is on). After leaving the computer for 30 minutes, I did a forced shutdown (with the power button) and I disconnected the external hard disk and network cable. Then I restarted again. But the screen is still dark and I cannot hear any noticeable hard disk activity.
What should I do?

 

[bozzykid]

Are you using HDMI? I had to re-set my HDMI cable after bootup for the screen to come up.

 

[Porcinet]

No I am using DVI. But resetting it won't change anything.

 

[Porcinet]

Surprisingly the computer just restarted... but the screen is still black

 

[Porcinet]

I rebooted using the Lion DVD and repaired the hard disk (there were some problems apparently). Now everything seems to be OK.