Help Nexus S won't sync contacts anymore

[Mrtn]

Hi everyone,
all of a sudden my Nexus S on 4.1.2 has stopped syncing my google contacts. And only my contacts, see screenshot below. No changes to settings were made, this came out of nowhere.

Does anyone have any idea what's going on and how I can solve this?
This it what I've tried so far:
- Turning the phone off and back on
- Unchecking the box and re-checking it
- Options - "Sync now" makes everything in the list sync except my contacts of course

Thanks in advance!