[TYPO3] Problems with fe login when switching T3-4.0.4 -> T3-4.1.2

[Michael Rolli]

Hi list

I'm confused and don't know where to start my debug journey because  
nothing seems to be an obvious or possible reason.

I have a Typo3 Installation running Version 4.0.4. It's running  
smooth and stable. In the particular interest of fe-login I use  
newloginbox, sr_feuser_register and sv_login_redirect. Everything  
works so far.

Now I wanted to update Typo3 to 4.1.2 because I have to use IRRE.  
So.. I got the typo3-4.1.2-sources, unpacked them, replaced the  
symlink (typo3_src -> /srv/libs/typo3_src-4.1.2) in the project  
folder, runned the installtool->update wizard, purged the typo3conf- 
cache (even with rm typo3cof/temp_CACHED*) and the FE cache.

Result: No fe login possible anymore. Any l/p pair is denied though  
right.

Switching back the symoblic link to Typo3-4.0.4 (typo3_src -> /srv/ 
libs/typo3_src-4.0.4) makes it work again without even purging any  
cache. :-)

Has anybody any idea where to begin to search? Anybody a hint what  
could be the cause of this? Has anything changed about authentication  
which I have to consider in my configurations? I didn't read  
something in the release notes.

Thanks for any help in solving this issue.
Regards
Michael