Context Menu Difficult to come up - TreeView + Nodes

Question

Its hard to come up with a subject title for this... 
 
But basicly this is what happens
 
i have a normal context menu attacked to a treeview with a bunch of treeviewnodes in it. so when u right click a node the context menu comes up,
 
however when you right click it dosnt always work, actully it never works at first you have to right click 3 - 5 times before the menu will display...
Any thoughts?
Thanks!