This isn't so much to fix your problem but to help others fix it.
It's a good idea to post some information here both on your system and the problem itself, people aren't psychic.
Note your hardware etc.
Where/how you got the live eval (if you burnt it yourself maybe it was a bad burn)
If any error messages come up before the black screen.
If any warnings are issued as it loads etc.
With this it means people can give more precise accurate answers, and you'll be able to fix the problem alot sooner.
Off the top of my head though, if you burnt the cd yourself, try burning it at a slower speed (it already boots, so you must know to write it as an image) maybe try a different drive in the same machine if you have one. Maybe it's a graphics card issue, in which case do you have another one/onboard to try??