Can't begin to guess. I've never had any similar problems.
Well...maybe I do have a weird possible answer.
If you have already written any content to the browser and then flushed the output buffer, then Response.Redirect can *NOT* work. But if you have an ON ERROR RESUME NEXT in place, then you won't get a message about it not working. It will just silently do nothing.
It doesn't sound to me like your problem, but...
I don't suppose you can show this at a live URL?
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.