Unconfirmed transactions from mining pool from 2015???

[kodiak1120]

Back when I was mining bitcoin, I used Eligius.  I've gone through one of my old addresses, and I found several unconfirmed transactions.  I only ever mined with Eligius and CEX.io, but I think this was from when I was mining with Eligius.  So this payment would have been a payout from mining, which is why I'm confused that it's referenced as a "double spend."  How can you double spend newly generated coins? 

Here's the transaction: https://blockchain.info/tx/2b8aa01242c3204d52e65a86e4ab2d8c963d4cb4b07ae00a9da74e5f0112fea4

I'm totally confused.  Can anyone explain why these transactions are still unconfirmed?  Am I out those amounts or is there anything I can do?  Thanks.

[achow101]

The block that that coinbase transaction was for became orphaned/stale. Thus the transaction is invalid and unconfirmed. Coinbase transactions only become spendable (and thus actually confirmed) after 100 blocks have build built on top of the block that the coinbase transaction is a part of.