Thinkpad Edge E335: Empty screen after login

[^rooker]

A brand new Thinkpad Edge E335, freshly setup with Xubuntu Precise (12.04) 64bit, has a weird issue:
When I try to login with a fresh user: it works.
When I try to login with the same user again: I only get the background image and then nothing else happens.

I could Ctrl+Alt+F1 into a terminal in order to reboot the machine.

So I've deleted all ".*" files in my home folder to reset the configuration:
Worked!
Once.
When I tried to log back in again, it took ages until the XFCE panels came up. Way too long.
After logging out again, the screen went black. The mouse-cursor stayed and was still moveable, but nothing else.
Ctrl+Alt+F1 still worked.

So I checked dmesg, and got strange apparmor="DENIED" messages, followed a:

segfault at 20 ip 00007fa0d2405af0 sp 00007fff628c57d8 error 4 in libdbus-1.so.3.5.8[7fa0d23e3000+42000]

to be continued...