the good news is: turnig off the screensaver helped with the freezing.
the bad new is: In the core I have an onboard realtek8169S...which I must have killed off somehow during the installation-frenzy for the eee box. Now after a reboot of the core my internal network is gone and I'm rather clueless as to how to get it back. I went to /lib/modules/2.76.22-14-generic/kernel/drivers/net and renamed the r8169.ko.not (which I renamed before following the wiki) back to r8169.ko and rebooted, with the faint hope, that this would bring back my nic...which it didn't.
So I'd really hate the idea of reinstalling the whole stuff again...so I'm hoping that some magnificent mind would kindly help me reviving that card...
[update] its in the middle of the night over here, so maybe I should use that to start an install again. I guess I probably fubared the whole thing already...so maybe I fresh start will do. I just hope I won't get too much trouble with r8168 and r8169 drivers. So I'll just hit the hay and when I get up the core should be waiting for me. The bright side of this is maybe I'll get some routine in building a core :-) At least I can keep my /home, so I guess I won't loose too much data.