In the syslog i also found the following errors:
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: SCL pin should be low
Jan 1 01:28:50 kernel: ***RTC BATTERY FAILURE***