I just recently bought a PS3 from someone. When I boot it up, I notice some blue balls/orbs and other blue objects appearing around the menu and loading screens. Is this a faulty video cable, or the console itself?

Also, it froze at the menu, and while doing a system update. Powering it off, than on fixed the issue.

Are the blue orb things the console screwing up, or the video cable being faulty?
Lastly, how can I do a system update without getting a black screen? I'm not in the mood to have another heart attack.