[TYPO3-english] Old BE (alt_main.php) loading after login

[Thomas Meixner]

Hi Albert - I remember the same happening on an updated installation 
4.0.4 - 4.2.3. I don't remember the exact solution but it had something 
to do with an Extension. Do you have any extensions which do FE user as 
BE user or something? I think it had something to do with FE Editing. 
Try disabling extensions one by one until you find the culprit.

Good luck
Thomas

Albert van der Veen wrote:
  > - If I have the default options 'backend,frontend' for the option
> 'interfaces' in the Install tool and login at the BE, I get redirected 
> to alt_main.php, which is the old backend. This isn't functioning 
> however, clicking on any menu items gives a javascript error: