vedi che l'inghippo c'è:
http://support.microsoft.com/kb/283185/EN-US/

c'è coso da capirci qualcosa ....ma nessuno sapeva niente?
Internet Exploer 6 now requires sites that set cookies to have P3P policies.

From the Microsoft page:
"Internet Explorer 6 implements advanced cookie filtering that is based on the Platform for Privacy Preferences (P3P) specification. By default, Internet Explorer 6 blocks third-party cookies that do not have a compact policy (a condensed computer-readable privacy statement) or third-party cookies that have a compact policy which specifies that personally identifiable information is used without your implicit consent. First-party cookies that have a compact policy which specifies that personally identifiable information is used without implicit consent are downgraded (deleted when you close Internet Explorer). First-party cookies that do not have a compact policy are leashed (restricted so that they can only be read in the first-party context)."

See:
http://support.microsoft.com/default...260971&GSSNB=1

For more about P3P:
http://www.w3.org/P3P/