You can quite efficiently get around memory limitations on 64 bit Matlab by using memmapfile. An entire day's worth of TAQ data should not be a problem.
there's some cool ones coming up soon http://www.pgm-class.org/ http://www.infotheory-class.org/ http://www.game-theory-class.org/ http://www.nlp-class.org/ http://www.crypto-class.org/ http://www.algo-class.org/