I have implemented a private ethereal blockchain. I have also deployed a simple trading smart contract. It runs fine once deployed through MIST wallet. The problem is that it does not subtract ether from the buyer's account and also does not add the ether paid by the buyer to the Seller's account. Once the Buyer's Contract Transaction is mined, the status in MIST Wallet while receiving the mined confirmations, does show that -120 ethers (e.g it is the cost of a product that buyer has paid via payable function). What can be the reason that MIST wallet is not adding or subtracting ethers from wallet accounts based on smart contract transactions?