I like your idea for an RMB->Move, you should create an IDEA on our ideas website so that it gets tracked (http://mentorideas.brightidea.com/iesd).
As for why is it sometimes working and not other times, I think it has to do with wether you are "stretching" the bundle end (you see the cursor change from a four arrow vs. two arrow cursor), if you stretch (two arrow cursor normally associated with resize) then it lets you join the bundle. If you move the bundle (four arrow cursor) then it just moves it.
Indeed, verifying that I had the two arrow symbol (stretch) was the culprit for joining nodes. The operation seems rather odd- I would hone down the cursor so i'm draging the node, not the entire wire, but now also have to pay attention for the move or stretch option for the node.. I can't imagine a real use for the move, but then again, my knowledge of VeSys is still pretty limited.
Thank you for the answer.