Okay, everyone cool down. We need a few things here. WP 2.2 may have adjusted the code, but the problem is WP 2.1 and _that_ is what is available for public consumption and support.
So, let's get this:
1) Plugins installed and versions
2) Theme used
3) Firefox extensions used, perhaps
4) Platform info... Windows? Mac?
5) Can you reproduce on a different computer?
After that, disable ALL plugins - particularly ANY plugin that MIGHT have javascript in use. Does this solve this problem (Note: it will probably create errors on the template because now plugin functions aren't available - don't worry when you reactivate those things will be fixed).
If that fixes the issue, take the divide and conquer approach and reactivate half your plugins (that you were using). Does the problem come back? If no, activate half of what's left. Repeat and rinse.
If you activate plugins and the problem does return, focus on that group of plugins. Deactivate half of them and check for the problem. Does it occur? Yes? No? And so on until you find the culprit.
If none of this solves the issue, kick your theme over to Kubrick (though I doubt this is a theme related issue since the error is in wp-admin but for due diligence, follow through and check it out).
I am 99.999% sure you will find the culprit.
Be methodical. Provide detailed info on how to reproduce.
And for God's sake, smoke a cigarette or drink a beer and everyone cool the tempers.
:)