TYPO3 Core

Trying to install extensions under 6.0.x, I got the following mistake:

The auto-installation after downloading fails plus empty entries in LocalConf.php. EM doesn't show the extension list either. Re-starting EM and manual installation attempts result in this:

Under 6.0.1, I got everything installed after several tries, while installation under 6.0.4 completely fails. De-installation seems to work, but Re-installation under 6.0.1 completely fails as well. Strange: "full" entry in extArray at LocalConf.php for news system even when it's de-installed (no other attempts, this was strange enough ;-) )!

The message in my log which led to refused installations is this:

Core: Error handler (BE): PHP Warning: Invalid argument supplied for foreach() in
/home/www/typo3_6.0.4/typo3/sysext/extensionmanager/Classes/Utility/DependencyUtility.php
line 145

-> first attempts where tt_address 2.2.3, tt_news 3.4.0 Beta and site crawler 3.5.0, but it seems to be a general problem since other extensions failed too

Additionally under 6.0.1, while the green light of another extension (bt_simplecontact) light was on and the extension worked, the entry in extArray was empty ! But the update to 2.6.2 I ran that evening showed no errors...it's still usable (and listed in the extList), but has an empty entry in the extArray
of LocalConfiguration.php.