This transaction:
Status: 0/unconfirmed
Date: 2014-04-05 23:57
To: M9rZQzcZk4ixPWW8xhbK5ynBA9fnKva9k2
Debit: -1900.00 MTS
Transaction fee: -0.0039 MTS
Net amount: -1900.0039 MTS
Transaction ID: 77dcf6653887cc45a8ae45c48921fa55f4898914723fb6a570e97914a6fe4140
Contains alot of coins from girigo`s pool and now it refuse to go through, a transaction that was sent after that one that only contained Ypool coins already have 20+ confirmations and is all dandy, beware!
I had the same problem in the beginning. Rebuild your wallet and raise the transaction fee you pay and the problem will go away. The transaction was never really sent.