Firefox problem: JavaScript doesn't work anymore

Suddenly JavaScript doesn’t work on my Firefox 3.0.1 - and that means I cannot approve group members, suggest solutions to posts and much more.

Do you have any idea what might be wrong?

Problem solved. I found out that it was due to an update to my AVG security package. This morning it had been installing a new Toolbar. I had removed it both in IE and Firefox. But in Firefox I also had to disable it completely.