Remove the symantec while still in safe mode and see if that does away with your black screen and non responsiveness. you need to use a symantec removal tool to get rid of it though. If you'll tell me what symantec product you use, I'll find out what to use to get rid of it (I think the Norton removal tool works for all Nortons and Symantecs, but I want to be sure before I tell you to use it).
I use the free version of Avast! You can find the free download from the Avast website here
. There is a button near the top of the page for the free download. I use it because it was the one that AV I found that didn't interfere with my online gaming lol. Other folks like the free versions of AVG, Comodo, and Kaspersky. Avoid McAffee and Norton/Symantec, they dont' work well with Vista.