The application in question is written in Coldfusion 8 and has been used by office staff (PC Browser) and engineers (Mobile Phone Browser) without any problems of this natire. No changes were made to the application but this morning, all Mobile Phone Browser users got "The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server it accessed in attempting to complete the request." when they tried to logon.
To try to isolate the problem I made a few tests:
i) PC Users have no problems accessing the application
ii) Mobile Phone Users can access a simple "hello_world.htm" page
iii) Mobile Phone Users can access the logon challenge page
iv) If Mobile Phone Users make a logon error the logon test page works fine and returns the user to logon challenge
v) Mobile Phone Users cannot access the application if they logon correctly
My HUNCH is that there is a server between the Mobile Phone and the webserver that is (has recently become) very sensitive to the time it takes to build a page on the webserver. Point i) above indicates that the webserver does not have a problem. Points ii) to v) above are examples of pages with increasing complexity that will take increasingly more time to build.
Any insights will be appreciated!