In my debug.log I see a lot of the following messages (with different orphan block number):

2014-08-19 19:04:23 ProcessBlock: ORPHAN BLOCK 631, prev=00000000000000005ee64e8321c3c428a91f5acc60b3ee02eaf1159c68e7e95b

It even blocked the sync of my bitcoind for several hours until I manually restarted it.

I've found this thread about it, and it seems to be a real issue/bug: https://github.com/bitcoin/bitcoin/issues/4353

However, I don't really understand exactly what the problem is and if there is something I can do about it.

The bitcoind was running on a Mac Mini 2.3Ghz i7, 4GB RAM, 1TB HD. It was run after a fresh reboot and most of the HD is free.

Does anybody know what's going on there?

Edit: Actually, I just noticed the orphan block number is now always 751. It looks like it reached like a sort of maximum value.