(I'm cc'ing the list in hopes that maybe this will help others when deailing with custom error documents that aren't working under IE - there have been a few people having problems with login pages and some of the Apache::Auth* modules, and maybe this will help. If it's old news to everyone, I apologize)
Michael, I found something relating to IE (ain't MS grand!) and custom error pages not appearing under the right (wrong?) conditions... Basically, if "friendly http error messages" is turned on for IE 5.X+, your custom error page has to be over a certain size in order for IE to display the original and not it's own "friendly" version. The defaults for IE6.0 (don't have an older one to test with) are anywhere from 256 to 512 bytes, depending on the error code returned. I had a user who was having this problem on my site. Took me a while to figure it out too, since I always turn the pesky thing off on my systems. I eventually remembered there was a way to override them, and a quick search on MS Support site turned up the answer. Anyway, that alternate login script I sent to you needs a minor tweak - basically adding 512 spaces (as simple as ' 'x512) to both the refresh page and the actual login page, so as to prevent the "intelligent" code in IE from hiding the pages. It shouldn't be a problem for most login pages, but the refresh page I'm using to make http->https->http logins work didn't have anywhere near the 512 bytes needed. Hope that's useful to you somehow. Later, Jim