[TYPO3] cannot login to BE and Install Tool

[Walter Jenner]

Hi Everybody!

I have a strange problem, with my Typo3 Installation on an IIS Server
(Wasn't my choice). I cannot login neither BE nor to Install-Tool.

* I think the Server is IIS 5 on Win2003.

* mySql is 5.0.22
	sql mode = STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

	(should I try MYSQL4 for the sql-mode??)

* php is 5.2.0
	sessions are working, I've tested that already

* typo3 is 4.1.2


The database user has all rights for the typo3 database.

The BE-users I'm trying are existing in the database-table.

The install tool password I'm trying is correct, as I checked this in
the localconf.php. That I don't see the usual hint ("The password you
just tried has this md5-value: ") when I try to login, is also an sign
for me that the password is correct.

I set doNotCheckReferer = 1 as well as lockIP = 0

Another information which might be important: During the installation
empty tables where created, so I inserted a dump from the local
installation.

Last not least: JavaScript and Cookies are enabled.

Has anyone an idea? Any help would be apreciated, thanks in advance

Walter