Thanks for your help guys.
Opened it and checked the cables. Everything seems to be connected. Although I wanted it to run for some hours, cgminer restarted half an hour before. But anyway, same picture:

[Elapsed] => 2105
   [MHS av] => 64931.87
   [Found Blocks] => 0
   [Getworks] => 84
   [Accepted] => 499
   [Rejected] => 1
   [Hardware Errors] => 26
   [Utility] => 14.22

Temp1: 26
Temp3: 47

Ambient temperature is about 23°C.