Michel one thing about expires is the following if you are in diferent time zones then you can have a problem since what IIS is doing is putting a datetime for validation of the page so what is 5 minutes to the server can be several hours and five minutes to the client.
I hope that this explanation will help you if not and don't know what else I can tell you.

>>Michel has I said I don't know WWC bus ASP works the folloing way.
>>if you say response.expires=-1 this will mean that this call has expired so if you do a call to the same asp page with the same url the call is made to the server again you can also put response.expires=5 this will meant that this call is valid for five minutes.
>>What this is doing is telling IIS to creates an HTTP expires header indicating the time that this page will expires.
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>I did try on the server side to add that. It doesn't change anything.