Error 403 Failed to read heders Error for long-runningCFMAIL and CFINDEX command

I have two different pages with long-running scripts on which I am recieving
the following error: Error - 403 Failed to read headers to server:
XXX.XXX.XXX.XXX (80) (where x's denote our server's ip) Reason: Headers were
invalid or incomplete One of the pages does a CFMAIL to thousands of
recipients, and seems to run correctly even though the error shows up. The
second page runs a CFINDEX against a large set of DB results, and seems to
fail. I do not know if there is another timeout value to set somewhere in the
server settings, either within CF Admin or within the web server (IIS). I have
played with the Timeout Requests after (seconds) value on the Server Settings
page within CF Administrator. In both cases if I use a smaller set of
recipients or db results, the page executes without error, so I believe the
problem is the length of time required to run these. The scripts *should* take
5-15 minutes to run. I cannot find anyone else who is having this same
problem. Please help!!! -Funkdaddy