Unfortunately contacts has stopped on Galaxy S5
The error message, contrary to what indicated by others with a similar issue, does not mention Samsung Link.
My message say Unfortunately CONTACTS has stopped. If a turn off and on again the phone, contacts works for a few times only to stop again.
I use smoothsync for Cloud contact and never had a problem in the past.
Re: Unfortunately contacts has stopped on Galaxy S5
You could try going into Application Manager in your phone, finding the Contacts app, and clear cache. This usually takes care of most rogue apps, but if that should fail, try clearing data (just make sure your contacts ARE safely stored in the Cloud and that you're OK with re-syncing them to your phone as this option deletes all contact information from your phone and re-forces Sync, if available).
If you're using a 3rd party cloud sync solution, this COULD give you problems even if it didn't in the past.