Comment 117 for bug 164526

I've had this problem in FF3 but this time not related to iframe or overflow setting but because of disabling input for a moment.

If someone stumbles upon same issue, this may help:

Testcase to reproduce problem:
textarea.disabled = true;
setTimeout(function() {
  textarea.disabled = false;
  textarea.focus();
}, 0);

How to fix it:
textarea.blur(); // blur first
textarea.disabled = true;
setTimeout(function() {
  textarea.disabled = false;
  textarea.focus();
}, 0);