Problem with Blank screens

I am having a problem with my computer not allowing me to view You Tube music videos. It has worked fine until last night, now, all I get is a black screen. I think the system must have done an automatic update and the firewall must be blocking the videos but I do not know how to correct it. I have a Dell Inspirion 1500 with 2 G memory and Vista Business edition. Any ideas how to correct this problem?

Welcome
Probably the easiest way would be to make a system restore and then change the settings on the Windows Update to notify and not install.
http://www.vistax64.com/tutorials/76905-system-restore-how.html
http://www.vistax64.com/tutorials/120695-windows-update-windows-automatic-updating.html
Section 5

If the above steps do not work, uninstall and install flash player. It can be done from the control panel.

If the above steps do not help, what fire wall are you using?