Inline-Elements - font-crash

Why does FCKeditor does not accept this cutout ?

<p><font face="Verdana" size="2">Error<br/><hr/></font></p>

I know its not a clear source because font have must contained only inline-elements.

After you paste this in source-mode and go back to html-mode and then again to source-mode you will see a javascript-error. Save is no more possible.