>>That sounds strange. I'd like to think large sites like Twitter would take great care to adhere to Web standards, and work properly with major browsers.
>>
>>Have you tested using multiple computers? Maybe you know other Twitter users, you could ask them if they see the same problem (no, I don't use Twitter).
>>
>>You could also try a clean uninstall, then reinstallation of FireFox: http://support.mozilla.org/en-US/kb/Uninstalling%20Firefox
>>
>>Do you run your computers/browsers in the US-EN locale, or are you using something else?
>
>I run with the default. Yes, that is US-EN locale.
>
>I am pretty sure if I would reinstall both browsers, the problem would have went away. I suspect a bug in each browser. However, I would have waited for a new version to be released before doing so.
>
>When I tried to run it from others PCs, all of them were giving javascript errors on Twitter site. For that part, I would say it's on their end. Because, I tested from various points of location. From the East, and from two Terminal Server connections from two networks 1000 km away.

Hmm, isn't the JavaScript running on your browser?

Are you using any kind of antivirus product that might be scanning or scrubbing JavaScript?