Since IE10 has installed on my Windows 7 box, it is impossible to login into my application... It was OK with IE9 and it still OK with FF and Chrome.
The problem is that
I've found what happens, and it can be usefull for others. @Mark Ormston was not so far : Cookies set with path /cas are send by IE10 to URL beginings with /cas-services
In my case /cas and /cas-services are not in the same WebApp and each have its own JSESSIONID. Sending JSESSIONID created for /cas to /cas-services lead to the problem describe above.
To correct, I simply rename /cas-services with /app-services (I guess that everything not beginning with /cas should work).
JM.