I know that somewhere deep in the bowels of this forum someone else had this same question, but I can't find it so I'm asking again. In Sonar Platinum I can only open one plugin window at a time. As soon as I click on another plugin, the first one closes. Where can I find the setting to change this behavior? Thank you!

Some smaller plug-ins will stay, whilst ones like AD2 will close if you open another.
 
Also, can't dock a window back into the task bar after dragging it out...used to be able to drag it until it appeared blue and could then dock it...now I have to right-click and select dock it.

In Preferences-->VST Settings try deselecting "Recycle Plugin WIndows"

Turn off recycle vst plugins in preferences.

rcklln
In Preferences-->VST Settings try deselecting "Recycle Plugin WIndows"

Yes, thank you! That did the trick. That must be new. Or at least it's new that they set it to the default behavior.

Or click a plug-in's pin button to keep it open.

Anderton
Or click a plug-in's pin button to keep it open.

I just realized that that's basically what the "recycle" option does: it just defaults the pin to unclicked. Thanks!