Essaye cette méthode. Elle a parfaitement marché chez moi :
"I found this issue to whom it may interest :
Open your IE, copy&paste the following code into the address bar and click go
javascript:document.write(navigator.userAgent)
It will show you about your UserAgent value, just like 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)' or so.If you find something in a mass, that's exactly the point.
The first bit above is a bit strange (I don't understand what he meant by 'if you fing something in a mass' but it shouldn't really matter since this step is informational only. The following is the bit that matters:
Now, please open the Registry Editor (start->run->regedit), locate the subkeys as follows
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\User Agent\Post Platform
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform
Remove all values except (Default) in each 'Post Platform' key, restart your computer. All things should go right."
Si tu piges rien à l'anglais, il s'agit simplement de supprimer les deux clés du registre mentionnée plus haut après avoir ouvert regedit.