[TYPO3] Form tag gets destroyed

[Vlatko Surlan]

My form tag gets converted to <form. This is the exact way it happens:

#1 I toggle content to HTML mode in HTMLArea (<> button)
#2 I paste form code
#3 I togle back to wysiwyg mode and the form (it's just a button) 
displays nicely
#4 I press the save button and once the page reloads the form comes up 
like this:

&lt;form action="https://www.2checkout.com/2co/buyer/purchase" 
method="post"&gt; &lt;input name="sid" value="xxxxxxxx" type="hidden" 
/&gt; &lt;input name="quantity" value="1" type="hidden" /&gt; &lt;input 
name="product_id" value="1" type="hidden" /&gt; &lt;input name="submit" 
value="Buy from 2CO" class="input1" type="submit" /&gt; &lt;/form&gt;

I found some indications that it has something to do with lib.parseFunc 
and lib.parseFunc_RTE but I have failed to get it working with some 
dozen setups.

Can someone please verify this behavior on the vanilla installation 
typo3 4.0.2? Only modification I made to the editor was to display all 
buttons.

Thanks in advance.