Loose RB 300 Tonearm Stem

I posted this in the Lenco thread but am looking for general help here.The part where the stainless steel stem of my RB 300 tonearm stem joins the plastic under-carriage of the arm seems to have become slightly loose.This has the effect of allowing the arm to move from side to side even when the base-nut is tightly holding the tonearm in position.Does anyone know of a fix for this?
Stefanl, there are 2 screws holding the anti-skating housing to the base. It sounds like yours are loose. This happened to me, and it is a relatively easy fix. The hard part is to find the screws! They are normally covered with plastic plugs and blend into the surrounding area so they can be hard to find.

I used an exacto knife to pry mine out. Unfortunately, I damaged one of the plugs and have not put them back in, but it is cosmetic problem only, and a very small one at that.

See the picture at the link below: http://s93813957.onlinehome.us/mediac/400_0/media/16016.jpg
One of the screws is visible just above and to the left of the "Basis" decal. (my arm is oem basis rb-300). The oher screw is to the back and right, on a diagonal from the other.

Thanks again to garth for helping me figure out my problem.
Thanks very much for that info.I had searched for those screws and had not found them because they are very well camouflaged.Yes that was the problem,they had worked loose and only needed a little tightening.Now I have a rigid tonearm again.Thanks again.