Eventually You could try the selective start up -- disable all services AND elements relating to iTune and QT and see if Poser starts normally. The point is there is a chance that when You need iTune and start it manually it'll load just what it needs. Could be the best compromise...

If I'm not wrong Poser has the ability to produce QT movies, so my guess is the problem arises because Poser looks for some QT stuff when it starts. If it's so the problem could be avoided if we prevent this (and we are not going to make QT movies!), whithout the need of uninstalling/disabling iTune+QT, the question is: can we?