Files are not uploaded

Hello.

My configuration is drupal 4.7.4 working on Apache/PHP/MySQL/Windows XP.

I've a similar problem that I cannot solve even after having spent a lot of hours on it...
I supposed this is a mod_auth_sspi issue although it occurs in Drupal environment.

I have two configurations both on the same XP Pro machine with SP2.
The first one is using Apache 2.0.58 and mod_auth_sspi 1.0.4
The second one is using Apache 2.2.4 and mod_auth_sspi 1.0.4

On both configuration, my site is using drupal-4.7.4 with webserver_auth module.

Using an admin account (not the admin one but one who has administrator rights) files upload works fine with the second configuration but with the first one, files are neither uploaded nor attached (not shown in the files list after clicking onto the Attach button).
With the first configuration, using Firebug expension with Firefox show a 401 http error (unauthorized) but I don't see what is the problem with authorization since I only switch between the two environment on the same disk where every directory has the same security properties !

I tried to use mod_auth_sspi 1.0.3 but I have the same problem. So I suppose this is a drupal problem.

Is there a limitation in drupal upload (may be due to ajax technique) in version 4.7.4 ?

Thanks for help.

Michel.