I developed a little .ashx handler that returns an image so I could do
<img src="myhandler.ashx?query=string">
It worked perfectly on my dev machine. I moved it to the production server (IIS on Server 2008) and it broke. By "broke", I mean it no longer returns a valid image. The handler calls an external application to generate the image - I had the path wrong, fixed it, and all that accomplished was to make the warnings stop showing up in the event log.
I know it has permission to run the program. I manually ran the command I'm passing it and successfully generated an image. There are no errors in the event log and the IIS log says it responds with a 200/OK. I'm a little lost as to how I should go about debugging this further.
So, got it solved.
The discrepancies between my dev environment and the production server led to the need to double-escape a special character that .NET is fine with but my external program interprets specially. The entire problem was unrelated to the handler.
Thanks for the help, though.