Sometimes I've had to set the midi channel to one instead of none and that would get some Cakewalk VSTs to sound again. Normally the channels route themselves.
 
Just noticed your post about the corrupted MIDI tracks. I have seen that before with old projects where the MIDI for some reason is not compatible.

I can replicate this problem...just load an instance of Kontakt but don't check the options to create MIDI and audio tracks. 
 
Different libraries react differently to this situation. Shimmer Shake Strike comes up with the blank UI described in my original post. Orange Tree Samples and Spitfire libraries displayed a "library not initialized" error message. Most others load without complaint. Kontakt then becomes unresponsive when you try to close it, making it impossible to properly exit out of Cakewalk.
 
Only Kontakt behaves this way, and only specific nki's. Other samplers, such as Superior Drummer 2/3, don't have a problem with you instantiating the plugin before attaching it to any tracks.
 
The solution is to always create and route the MIDI and audio tracks before loading an instrument. Or just let Cakewalk create them for you automatically (which I often don't do, but will from now on).
 
 

Its just bapu messin with u.

I get this too with Orange Tree Samples!  Seems to be related to not having at least one audio output routed to the instrument though.  I don't think it needs any MIDI.  Which kind of makes sense, Kontakt the plugin doesn't know what format the audio is supposed to be so the scripts get inited differently.  Though I didn't have any trouble adding an audio track and routing Kontakt to it, which caused OTS Stawberry to init correctly.  And I didn't see a hang when I tried to exit.