Not wanting to insult your intelligence, but since nobody else has asked it I will; you ARE using the QR properly, right? That is, are you closing it by turning the cam lever over center as opposed to using the lever like a wingnut and winding the QR closed?

This page shows the correct procedure and also the enclosed cam mechanism shown is the only kind which will clamp satisfactorily. How To Use Bicycle Quick Releases

prathmann's comment regarding axle length/protrusion is worth checking out as well.