IIS - Other - Office 2007 file integration

We're having problems with an IIS6.0 server running ASP.NET 2.0 when downloading Office 2007 file types. We have updated the Metabase.xml file with the required mime types. The server still sends the file as .zip.

I believe the reason is the server sends a Content-Type: Text/HTML in the response header, even though it has the corrrect mime type. Does anyone know where this could be possibly coded? Here's the response header:

HTTP/1.1 200 OK
Date: Fri, 14 Aug 2009 19:36:23 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
Cache-Control: private
Content-Type: text/html
Content-Length: 379616


Here's the request header:

GET /client/ReportServe.aspx?filename=998~MGA/April%2020,%2020091.xlsx HTTP/1.1
Accept: image/gif, image/jpeg, image/pjpeg, application/x-ms-application, application/vnd.ms-xpsdocument, application/xaml+xml, application/x-ms-xbap, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*
Accept-Encoding: gzip, deflate
Cookie: ASP.NET_SessionId=h3q0vzvcp3znf145gooo5j45; WebSvrTrack=key=e288029b-fe9d-4b95-af75-9c6500e027b7; .FormsAuth=F07943769C9B131582414A3A37AF679451DD038 F93BA114DA6E66FB9BCF8C889A8513EDF044D04439B843515C 9937F3ADE82FC7910136AFA230EE715D955507EE9385B90B9F BC8BE0E2127010DDF94FE
Host: websvr.example.com
Connection: Keep-Alive
Accept-Language: en-us
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; U

It shows as zip whether I'm using IE, Firefox, Safari, etc. TIA for any help.

OI_Guy