Thanks for the help Bill, but Rick guessed that the code was choking on the InnerException.ToString() for some reason, and that turns out to be the case. If I use the Message property instead, everything works as expected.

Unfortunately, passing this info to the redirect page is just for testing purposes - what I want to do is *log* the error information, but if the Application_Error is going to choke when I try to retrieve this, then I'm going to have trouble <g>. See my response to Rick for all the gory details.