Firefox 3 and Twitter

... don't work well with each other.

For some days now (I feel that it was with the 3.0.2 or 3.0.3 update from FF) whenever I type into the twitter status input field, it slows down, grabs 100% of the CPU and I can type at a rate of 1 character per 2 seconds !!!

It seems that the javascript for updating the counter for the remaining characters (just right above the input field) is doing this, but I cannot really prove this.

Strangest thing is, it does not do this with IE or with the very same FF version running in a virtual box (different profile, though). I also started FF without any extensions (firefox -safe-mode) and disabled spell-checking.
No difference.

Could not find any hint or reference to this behavior on Google.
Strange.