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Hello Doug,

Based on our conversation earlier today, I am closing your case at this time. It was truly a pleasure to work on this challenging issue with you. As mentioned over the phone, I would be going ahead and processing a refund for you for this case.

It is very important for us that you to be able to rate our service as excellent. If at any time, you are not happy with the service that you have received on this case, you can provide feedback directly to me or my manager at the contacts listed at the bottom.

Here is a summary of the key points of the case for your records.

Problem
===================
Intermittently the server does not serve up static content. Images (JPGs and GIFs) appear as a Red X.

Troubleshooting Summary
===================

At first it appeared that we are running into a hang issue. However, on determining that we are able to get to simple pages from different clients, we were able to confirm that the IIS process are in fact responsive and hence this is not a hang.
Removed the unnecessary websites from the IIS metabase using the IIS Admin tool – since IIS 5.1 supports only 1 website running at a time.
Found HTTP 403 error being logged in the IIS logs.
This appeared to be occurring due to the fact that the maximum number of client connections has reached (i.e. 10 connections) and hence IIS cannot accept any more connections.
Took a perfmon log and noticed that for each request, the connections attempts per second goes up by 14 (1 for the html page, and 13 for the 13 images on the page).
During a failure, the number of connections attempts per second would be fewer.
Turned on HTTP Keep-Alives, and now a connection is re-used to serve requests to one client, thus resolving the HTTP 403 issue.
Now we noticed HTTP 500 errors on JPG, GIF and other static content.
Removed the JRUN ISAPI filter and uninstalled Cold Fusion. Problem persists.
An HTTP 500 is indicative of failure on the server when it is trying to execute some script (such as ASP, VB Script) on the server side.
Ensured that no ISAPI extensions are configured for JRUN.
Ensured that no ISAPI extensions are configured for JPG/GIF extensions.
Ensured that ASP Server side debugging is disabled.
Turned off Allow IIS to control the password.
Installed the IISMon filter, which seemed to resolve the issue. Could be due to the fact that IISMon does extra processing, thus reducing the speed with which requests are processed by IIS.
Removed all standard ISAPI filters and restarted IIS. Problem persists.
Uninstalled IIS and re-installed. Problem persists.
Stopped all 3rd party services and processes.
Ran TCPView from sysinternals.com, which showed that only 4 connections were open on the server using port 80.
Created a simple html page with a bunch of images and stored this under the default website. This fails intermittently as well.
Verified that the content is not being picked up from a UNC share – to ensure that this error could not be occurring due to failure during network access.
Verified that content expiration is not enabled.
Enabled extended logging in IIS and noticed that HTTP 500 is logged in the IIS logs, with Win32 status of 6 i.e. ERROR_INVALID_HANDLE.
Gathered a set of netmon traces when reproducing the issue and this confirmed that “Handle is Invalid error”.
Noticed that for each request to the web server (html or jpg / any other static content), a corresponding file is created in the C:\ folder.
Verified that this is not natural behavior in IIS 5.1 – by confirming the same on my machine.
Gathered a set of hang dumps of the inetinfo process, and this showed a 3rd party component from ByteMobile installed i.e. bmnet.dll. Removed the PCS Sprint Connection Manager to which this component belonged, and restarted IIS.
This resolved the issue.

Cause
===================
We found a component of the ByteMobile software that was being loaded in the inetinfo process and causing this failure. This component appeared to be caching each response to the disk before sending it to the client. This was causing the server to run into the HTTP 500 error with Win32 status code 6 (Invalid Handle) thus resulting in a red X being displayed for the failing image.

Resolution
===================
Uninstalled the Sprint PCS Connection Manager and this resolved the issue.

Please let me know in case you have any follow up questions regarding the documentation above.

I hope that you were delighted with the service provided to you. It was truly a pleasure working with you and I’m glad we were able to persist with the troubleshooting and resolve the issue. As an added benefit, in case you have not already reviewed them, I’d like to offer you some Knowledge Base articles that have proved very helpful in general. Let me know if you have any follow up questions.

How to debug ISAPI DLLs in IIS 4.0, IIS 5.0, IIS 5.1, and IIS 6.0
http://support.microsoft.com/kb/183480

HOW TO: Use Wfetch.exe to Troubleshoot HTTP Connections
http://support.microsoft.com/default.aspx?scid=kb;%5bLN%5d;Q284285

IIS Insider
http://www.microsoft.com/technet/community/columns/insider/iisiarch.mspx

How to use the Debug Diagnostics 1.0 tool to analyze a memory dump file
http://support.microsoft.com/kb/921464

Tools and Utilities to use for Troubleshooting
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/bts06coredocs/html/c817384f-e328-439d-9c41-a94ed75670ce.asp

IIS Diagnostics Toolkit (x86)
http://www.microsoft.com/downloads/details.aspx?FamilyID=9bfa49bc-376b-4a54-95aa-73c9156706e7&DisplayLang=en

Internet Information Services 5.1
http://www.microsoft.com/windowsxp/evaluation/features/iis.mspx

Securing Internet Information Services 5.0 and 5.1
http://www.microsoft.com/smallbusiness/support/articles/sec_iis_5_0_5_1.mspx

A Look at IIS 5.1 in Windows XP Professional
http://www.microsoft.com/technet/community/en-us/windowsserver/articles/art_iis5inxp.mspx

Thank you and have a wonderful day!
Best Regards,

Rohan Makhija
IIS / ASP.NET Support Engineer