InformAction Forums

On this forum: http://www.radforum.de the login is not handled by password manager, as long as NoScript is enabled.

Nope, it's that forum which breaks the password manager unless scripts are activated.
In facts, when you load the page the username field comes pre-filled with the "Benutzername" string. Since the password manager expects to find the fields to be processed empty, it skips that form.
If you've got scripts enabled, a script in the page clears the username field before the page loads, and therefore the password manager finds it empty and processes it normally.
Possible work-arounds:

1. Allow radforum.de - it's the simplest, but you may prefer...
2. ... asking the site administrator to eliminate his useless "Benutzername" prefill

Thanks for that quick reply. This is a problem, that doesn't occur only in that fornum.

Where else does it happen?