We develop and host a webbased accounting application which is fully xml/xsd 
and webservice oriented.

We have recently noticed that xml schemas (xsd or xdr) are not being cached 
by Internet Explorer, or at least the cache isn't being used anymore. We know 
for a fact that this was working properly until recently: if-modified-since 
headers would be sent to the server which then replied with 304's, but now we 
see that these headers are not being sent anymore, forcing the server to 
respond with a 200. We suspect it must be due to some recent windows update 
(urlmon, wininet, msxml ??) but we're not exactly sure when.

When the schema is directly requested through the location bar of IE it is 
cached correctly while if the xml parser is allowed to resolve it as an 
external the cache is by-passed (no if-modified-since header).

Our XSD is over 140kB and caching is obviously crucial to the performance of 
our application.

Any comments, suggestions, similar experiences?


Thanks in advance




--------Sample XML-file:---------------
<?xml version="1.0" encoding="utf-8" ?>
<DATA xmlns="x-schema:schema.xsd">
	<CUS>
		<CUSNBR>1</CUSNBR>
	</CUS>
</DATA>



--------Sample XSD-file:--------------
<Schema xmlns="urn:schemas-microsoft-com:xml-data" 
        xmlns:dt="urn:schemas-microsoft-com:datatypes">
	<ElementType name="DATA" content="eltOnly" order="many">
		<element type="CUS" maxOccurs="1" />
	</ElementType>
	<ElementType name="CUS" content="eltOnly" order="many">
		<element type="CUSNBR" maxOccurs="1" />
	</ElementType>
	<ElementType name="CUSNBR" content="textOnly" dt:type="int"/>
</Schema>