I have a complicated problem that I will try to explain.
We have a portal based website that is accessible from outside of our organisations infrastructure via username and password. Certain types of files are not accessible on the website to certain people in certain locations. The problem is not user specific; in sites where you can access the files, you can do it as any user, in sites you can not access the files, you can not access them on any user. The sites that can access / download the files do not appear to have anything in common - some work from some corporate buildings, some dont, some work from some home networks, some don't.
The only common factor I can see, is that when it does not work, it is for specific files only. Mainly .doc .xls .ppt .gif.
The mimetypes in IIS appear to be setup correctly and have not changed.
The setup of the server side of things is quite complicated.
There is a front end server that serves most pages, when one of the images (gif - jpg work fine) or a doc from the page are called, you either get an image placeholder or a gateway not found message. The files that are called, reside on another webserver which has a virtual directory on a further seperate server (a nas device).
The 2 webservers are Windows 2000 (iis5) and the nas with the data is windows 2003.
This is a new problem, up until now there have been no similar issues since the inception a couple of years ago.
Nothing obvious is showing in any of the event logs
IIS logs don't show anything obvious either - in fact, I have compared the get commands from a number of different client requests and all match up just fine - ie ones that work look like ones that fail.
Another thing to bear in mind, is that the system must know the file is there, as you get a bad gateway error. When testing with a fake file that doesnt exist, you get a 404.
I am sure there is info I have missed or you will need, to help me, so please ask.
I look forward to your ideas and responses.