Update mechanism not working all of a sudden

I’m using wordpress for more than a year now, but since today the update mechanism isn’t working anymore. I have to wordpress blogs hosted on my own VPS, they are set up on different Apache VirtualHosts with different domains and everything used to work fine. Since a few weeks I used W3TC on one of the two blogs together with PHP APC without any problems. Today I had some caching issues (preview not updating with changes) when I wrote a new post and therfore did some research on W3TC. I read that it would be best to have minify not using APC but do its minifying stuff on disk and so I changed that setting. Then I got some weired errors telling me that the .htaccess file is not using fancy permlinks (though it does) and that page cache might not be working correctly. I then wanted to update all packages to the newest version, just in case, and while updating the packages it got stuck and didn’t move on for like more than five minutes. I couldn’t even load any other pages anymore on said blog but changing to another browser on the same machine worked. Now whenever I try to update a plugin it gets stuck at unpacking the zip file and the browser won’t respond to any link to the wordpress blog (though munin for example on the same domain works fine).

The interesting thing ist, that the other wordpress blog, I didn’t change anything at all, has exactly the same error too now. Sadly apache doesn’t log anything special at all.

Need help please!!

Greetings schneida