Text Tab, Help Button, Linking, HTML Not Working

We’re running the twenty-ten theme.

— Help button does not work.

— From the Dashboard, when you click Posts, then click edit on any post, you can see the Visual screen where text shows up and the post looks like the way it will on the web.

— If you try to click the Text tab in the upper right beside the Visual tab, nothing happens. You are not able to look at the html for the post.

— If we highlight text in the screen and click on the paper clip to add a link, nothing happens.

We are unable to add links or pictures or revise anything through the html screen, though just a few days ago we could do so. Please help?