There's some technical quirk whereby those coins, or at least a substantial amount of the earliest Satoshi coins, cannot be spent. Escapes me what that quirk is specifically, someone will probably remember before I find it in search though
Are you thinking of the genesis block coinbase?
There is a 50 coin glitch there, but I don't recall any other problems.
No, I'm using specific language like "at least a substantial amount of the earliest Satoshi coins, cannot be spent" because I definitely recall someone very technically knowledgeable saying that. I will have to look.