Stop eating "onclick" argument

Hi,

I've a content whose the HTML source code containts a link with an "onclick" argument.
When I copy the page content (not the source) and past this in a CKEditor textarea (in WYSIWYG mode), the "onclick" argument of the link disappears from the source.

For example, if I copy this page content : http://difoolou.net/bla.html (Ctrl-A & Ctrl-C) and paste in CKEditor (Ctrl-V), the HTML source code result is :

<tr bgcolor="#f3eedb" valign="top">
   <td class="TexteDeBasePetit" width="100">11/10 23:38:59 :</td>
   <td class="TexteDeBasePetit" align="left"><font color="blue">Tu donnes <b>1 PO</b> à <a style="cursor: pointer; text-decoration: underline;"><b>Le corbeau de Creasy</b></a></font></td>
</tr>

Instead of

<tr bgcolor="#f3eedb" valign="top">
   <td class="TexteDeBasePetit" width="100">11/10 23:38:59 :</td>
   <td class="TexteDeBasePetit" align="left"><font color="blue">Tu donnes <b>1 PO</b> à <a style="cursor: pointer; text-decoration: underline;" onclick='window.open("http://www.pirates-caraibes.com/fr/joueur/contactJoueur.php?u_i_perso=7044","pirat_ct_joueur","width=800,height=650");'><b>Le corbeau de Creasy</b></a></font></td>
</tr>

I tried with several versions of Firefox and with some versions.

It works with theses versions of Firefox :
- 2.0.0.12 (Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12)
- 3.0.0.10
- 3.6.8 (Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8)

But not with theses:
- 3.5.13 (Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.9.1.13) Gecko/20100914 Firefox/3.5.13)
- 3.6.10 (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.10) Gecko/20100914 Firefox/3.6.10)

What's happening ? How to solve this problem ?

Thanks for your help.