I have used Sonar X2 for quite some time now and am fairly comfortable with it. I've added nodes to an envelope many times and had no problems whatsoever. Until now.
 
For whatever reason, I cannot add nodes to an envelope on the track I'm working on. I can do it just fine on other tracks though. I've tried using various methods to insert a node, ie, the pencil tool and drawing them in, right clicking and inserting at selection,etc, but no luck.
 
Whichever method I use I get the same results. For example when I use the draw tool and try to insert a note on an envelope the upper left half of the Write Enable Parameters button turns red but no nodes are added. When I hover over this Write Enable Parameters button it will say the feature is turned on or off but changing this does nothing to allow me to enter a node on the envelope.
 
I'm out of ideas. Any help would be appreciated.

Is your edit filter set to clips or to the envelope you're editing?

Hit F5 to enable standard smart tool.
 
Hold shift and move the mouse over the envelop of your choice and click it to bring it into focus.
 
Double click on the envelope to add the node.
 
You can shift click back on the clip top to return the focus to the clip, or change the focus to other envelopes.

If those ideas don't work please post a screenshot.