I wouldn't think "enable script blocking" should make any difference to a program update, that's more to prevent dodgy items in hijacked or dodgy web pages from running.
What AV is it? And is it the same AV on both?
Ditto question the firewall.
Ditto question any other application eg antispyware/behaviour blocker etc.
I have to tell you I'm not an expert, but have troubleshot a few of this type of issue.
Is the primary, perchance, an HP or Compaq presario with AMD processor?