Veeam support examined the logs that showed that the underlying backup job block size changed. As a result the backup copy job could not identify new restore points.
[02.12.2014 00:03:21] <01> Info [OibFinder] Following Oibs are located in storages with different (KbBlockSize256 expected) block sizes and excluded from search:
[02.12.2014 00:03:21] <01> Info id='5af64457-e94a-4053-a166-e8319ad176ee', time='11/13/2014 10:21:17 PM', block_size='KbBlockSize1024'
The solution was to do an Active Full. This immediately fixed the problem.
This case is resolved.