For Firefox 2.0, there's an "Enable JavaScript" checkbox on the Content tab of the Preferences dialog; it should be checked.
But your reply sounds as if you're seeing this with multiple different browsers. If that's the case, then I wonder if it's not browser settings, but rather a piece of security software (like Norton or MacAfee), or a firewall at your office, that's set up to filter out all incoming JavaScript. If that's the case, then browser settings won't help.
Can you, for example, see videos on YouTube? Or if you go to this page:
http://script.aculo.us/ , do you see the following message?
"You really, really need to enable JavaScript to view this page".