We use a product called "OWA for PDA" by Lee Derbyshire.  If you haven't
tried it, i strongly recommend the product (particularly for Ex2k7 folks.)
The application is essentially an OMA replacement.  It optimizes OWA for PDA
and mobile phone screens.

http://www.leederbyshire.com/

In any event, my problem is this:  I've been using it for a while, until
recently when it started going directly to a page that says "you are not
authorized to use this page." and "you do not have permission to view this
directory or page using the credentials that you have suppled."  It appears
that mobile IE is caching my old credentials somewhere.  I say this because
i also have MINIMO and Opera Mini installed on my device, and they connect
no problem.  That's also why i doubt this has anything to do with the
application itself.  Even using IE on my desktop i can access the page
without issue.  It's just IE mobile that's stuck.

I've tried deleting all the temporary internet files on the device, as well
as cookies etc.  I've also deleted the bookmark and entered the address
manually.

The only thing i haven't tried is a hard reset, and i'm not going to do that
since it would wipe out my phone.  Are there files on the phone i can
manually delete that may contain that information?

This is a Sprint (HTC) Touch; WinMobile 6.

Thanks.