GetHttpRequestData missing "If-Modified-Since" and "If-None-Match"

[Chuck_ers]

I'm using CF8 on IIS6/Win2003 Server.

In my cfm I have:

<cfset reqheaders=GetHttpRequestData().headers>
<cfdump var="#reqheaders#">

...which gives:

struct
Accept	text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Charset	ISO-8859-1,utf-8;q=0.7,*;q=0.7
Accept-Encoding	gzip,deflate
Accept-Language	en-us,en;q=0.5
Cache-Control	max-age=0
Connection	keep-alive
Cookie	CFID=[removed]; CFTOKEN=[removed]
Host	[my test server]
Keep-Alive	300
User-Agent	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3

But if I look at the actual headers being sent from my browser (using Firefox LiveHTTP add-on), it shows I am sending "If-Modified-Since" and "If-None-Match" headers.

GET /path/to/cfmfile.cfm HTTP/1.1
Host: [removed]
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.6) Gecko/2009011913 Firefox/3.0.6
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: CFID=[removed]; CFTOKEN=[removed];
If-Modified-Since: Fri, 18 Sep 2009 01:18:19 GMT
If-None-Match: ""0134E50193C69AD753656B0513FCB28C""
Cache-Control: max-age=0

Is there some reason IIS would "steal" those headers before handing over control to ColdFusion?  Or does GetHttpRequestData sometimes "miss" headers?  Other ideas?  Is there any other way I can get at the raw HTTP request from within ColdFusion?

I'm at a loss.  Others have used the same process and no one seems to have this issue.

(see: http://www.petefreitag.com/item/235.cfm or http://admin.mxblogspace.journurl.com/?mode=article&entry=1853 for examples)

I've tried accessing the page using Internet Explorer instead.  It also is not showing those headers, but I have not sniffed IE's actual headers being sent so I can't be sure those headers are included (but I think they are, since IE implements conditional GET).

[Chuck_ers]

Found out the answer.  IIS 6 does in fact steal "If-Modified-Since" and "If-None-Match" headers, but only on custom 404 redirects.  That's actually what I'm doing here (that'll teach me not to put details in a question when I think they're irrelevant -- actually I just forgot).

Here's two discussions on the issue (they're using ASP, but apparently it's the same for ColdFusion):

http://www.eggheadcafe.com/conversation.aspx?messageid=32839787&threadid=32839787

http://www.webmasterworld.com/microsoft_asp_net/3935439.htm