I have Internet Explorer 5 and I can get into chat.
You can check your security settings if you:

1) Click on Tools on the top line menu
2) Click on Internet Options
3) Click on the Security tab
Make sure Internet is highlighted.
Note, my security level is set on Medium. If yours is on High and you reset it to Medium, it might do the trick. If not:
Click on the Custom Level button.
Look for Java, then Java Permissions
If Disable Java is checked, that's your problem. Mine's on High Safety, and it works.

I have to leave for work in a little while, and tomorrow I'm off to NOMAD. If you still have problems, maybe we could work on it by phone or some other way.