[TYPO3] Install Tool Login doesn't work

["Christoph Roethlisberger]

* Systembase is a Windows2000/IIS5 server with PHP 4.4.3 (or 5.1.4) and
MySQL 4.0.x (runs on an external linux box)

I can't login to the install tool once everything is set up. It's a very
strange behaviour, cause of I know the password is correct ;)

--- FACTS ---
- when you enter a false passwort it will say so and show the hash of it
- when you enter the correct passwort it doesn't show the hash value nor the
small text about it before
- in the webserver logs a wrong password produces 1 entry, a correct one 2
- if you enter the password as a GET value in the URL (i.e.
www.site.com/typo3/install/index.php?password=xyz) you will be logged in
directly and everything works
--------------

Normally I don't encounter any problems with typo3, but then - all my other
installations are on LAMP environments - but this one really breaks my head
As for the operation of the website, this is no problem, cause of I can do
the complete installation, (Typo3 itself calls the install page with
?password=joh316 the first time you hit the page) but it sucks afterwards as
the install tool is not "really" available anymore

Anyone ever encountered the same problem (google shows some positive hits on
this, but no answers....as always ;) and knows a solution?

best regards
Christoph Roethlisberger