[TYPO3-english] Can't login to BE after Update from 4.4.0 to 4.5.7 - frontend broken rootline

[Christoph Stadler]

hello,

i just tried updating my typo3 install to 4.5.7 ... here is what i did:

1 - updated all extensions, cleared caches and temp files in the 4.4.0 
install

2 - copied the contents of the source archive over replacing the old 
files/folders

_.htaccess
ChangeLog
GPL.txt
index.php
INSTALL.txt
LICENSE.txt
NEWS.txt
README.txt
RELEASE_NOTES.txt
t3lib
typo3

3 - disabled .htaccess

4 - went to the install tool and completed all steps of the update wizard

5 - compared database

6 - deleted temp files

the login page of the backend is now missing the CSS it seems, looks 
broken, and when i try to login i get back to the login page, without 
any error message, just the login dialog disappears

in the front end, i get the error: "The requested page didn't have a 
proper connection to the tree-root! (Broken rootline)"