Shall I worry about that ? 12:10:30 2016-02-20 [TRC] MINR: Skipping tx e2bb0e483add2bd4fdcea9f11138171a09166cd4badd21008b2de394658ab844 due to error in CheckTransactionInputs: transaction e2bb0e483add2bd4fdcea9f11138171a09166cd4badd21008b2de394658ab844 tried to double spend coins from transaction 8f8704f19ac9193dca91fb50587268e2105188d5e4112c8cd960e4a7cc13e649 $ grep -c "tried to double spend" dcrd.log 20446 I have found only one occurence in testnet daemon log.
It's nothing to worry about. It simply means that two transactions tried to spend the same coins so one of them was rejected as it should be.
MINR is the subsystem in dcrd that builds the block templates upon which the getwork is provided. The only reason you're even seeing those messages is because you have trace logging turned on as indicated by [TRC]. It's just reporting which transactions that are not being included in the block template due to them attempting to spend coins that are already spent. The most likely reason is that a new block candidate has shown up, but doesn't have enough votes yet, so the transactions that it includes are still in the mempool. However, the block template generation is noticing they are already spent via the candidate, so it skips them. There are certainly some things that could be done to avoid logging in that case (and my personal opinion is that they probably should), but that actual transaction selection logic is working properly.