I have actually seen this problem with a couple of lenses on the D300. It has happened with the 70-200VR1 and the 200-400VR1. I live and shoot in place that is always hot, so I don’t think temperature is the issue. On my D300 there is a little bit of play between the camera body and the lens and remounting the lens seems to fix it. The play might be the issue but I tend to agree that it is more likely the contacts. And, despite what I just said above, this could be caused by the heat and humidity because remounting (an actions which brushes the contacts over themselves) seems to fix the problem.
I don’t think it is the lens itself because the problem has not happened on the D3s which seems much tighter in the mounting than my particular version of the D300.