I may be mismembering, but if I recall, IIS wants NPH-style headers all the time. Maybe header() gets it right (autodetecting IIS and dumping NPH mode), but redirect() messes up.

time passes...

Hmm. Nope... redirect calls header, according to the source. Scratch that idea. Do you have a fairly recent CGI.pm?

-- Randal L. Schwartz, Perl hacker