Negative number of confirmations for a testnet transaction on blockexplorer
If you look closely on blockexplorer.com, you will notice that the site does mention that the transaction was included in block #1484064. The blockexplorer seems to be confused about the height of the blockchaintip, or has some other general issues regarding the confirmation count. For example, it shows all of the transactions in the latest block to have -3562 confirmations: 

The transaction in question has some 1300+ confirmations, so this seems to be squarely on blockexplorer.com.