Perhaps there is an external operation which is taking a long time to complete (such as a query) and the request is timing out as soon as it gets finished with that external operation. (CF doesn’t tend to notice timeouts if its waiting for an external resource since Java puts the thread to sleep while it waits) How much time is passing before it times out? If your time out is 60 seconds, is it erroring exactly 1 minute after it starts, or several minutes later?
Again, get a tool such as SeeFusion and sit there and refresh the stack trace on that thread while it is running to see what it is doing the entire time.
Thanks!
~Brad