Negative balance after sendfrom bitcoind
Read this issue: 
https://github.com/bitcoin/bitcoin/issues/2079

As  gavinandresen commented December 06, 2012


  Yes, that is a 'WONTFIX'.
  
  A sendall account  command that took the account to exactly
  zero might be a good solution, although you can still run into edge
  cases like "what if the account contains 0.000001 BTC" (fee to sendall
  might be greater than that).