problem with html tags in source mode

Hi,
I losing my mind and I can't solve this problem for 5 hours.
FCK editor simply disappears when I do something like that in source mode:

<strong>xcvxcvxcv
</strong>



I have to use phpmyAdmin and edit text there because it's not possible to do anything because there is no textarea. Of course when I write this way everything is ok...

<strong>xcvxcvxcv</strong>


Please, tell me what to do, I think I tried everyting

Greg