[Typo3] Strange behaviour after upgrade to last version

[Marc Valentin]

I use the multi language system and a frame based web site (based on an 
old typo3 sample). Here it is : http://www.anthonycharity.org/
The default language is english, and I show little flags to change the 
language at the top of the page.
My problem is that now, when I click on a flag (on the right frame) the 
left frame doesn't disappear. It remains there. You can try. Any idea why ?
Thanks.
-marc-