It's best to think of these as two things - they're related, but there's different dynamics going on with each of them. A key difference is Abyei is contested territory. We still do not know whether Abyei is going to belong to the new country of South Sudan or effectively the new country of Sudan, the northern part. That was supposed to be decided by a referendum in January; that referendum never happened, so it was being dealt with through political negotiations.