OWA 2007 published over ISA Server 2004 Button not working



We´ve published Exchange Server 2007 Web Access over our ISA by a
rule. Everything works in general, but when you log off from OWA,
there is a button to close the page. that is not working.

when you try to access OWA from the exchange itself, the button works.

any ideas ?

thanks in advance

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