hey there. This is the most weird thing. The transport is not working. When I press Play, The Play button does not turn blue, the playback starts but the Stop button stays grayed out and I can not press it. So I have to use Pause instead. When I press Pause, the pause button turns blue, the Stop button stays grayed out. I press Play again- then play button turns blue, and Stop button becomes normal light gray and I can use it. 
I have Kontakt instrument loaded- it is "Sequence" drum sequencer and it has Play button. I am suspecting it has something to do with it. The Play button in Sequence turns blue and responds every time disregarding of what I use- Stop or pause, the drums playback is on time and responds, but I can not properly use Stop button in Sonar transport. Any thoughts? Thank you. 

Still acting out- very hard to work. Any suggestions? Thank you. 

Just make sure when this happens that you close all 3rd party floating Windows ( e.g kontakt etc etc and the stop button shouldnt be greyed out anymore in the transport window.
This happens to me when I have a few Pro-C floating Windows open.

This can also occur if you have a VST preset windows explorer window accidentally left opened inside sonar , just look at the windows task bar and hover your mouse over the sonar icon to make sure no other window is left open .


Also the space bar will still function as a stop button when this occurs.


Good luck

Thank you for your replies. What windows? You mean Software synths that loaded in Sonar or the once that are Freestanding? I do not have any freestanding software synths opened, but I do have few windows opened of synths that loaded in this project. I never had this issue. I always have up to 10 Soft Synths open at the time. This is why I have 32 Gb of memory. 
 
I have a feeling that it has something to do with Sequencer receiving command to play and stop. But I may be wrong. I will close windows to see if it helps when I get home. This is very frustrating. It takes 6 clicks to stop playback. When I am in the middle of recording, I can not do this. This is a bug. Cakewalk should be interested in it and wanting to solve it. This is pretty big deal. This should not be happening dont matter what windows I have open. 
 
Thank you. 

This happens mainly with vst plugins that are not proberly programmed.
We use sometimes a plugin that is programmed by an amateur ("dynamic normalizer") with no GUI, that disables also "stop".

This started happening to me to where play won't work even with the spacebar. So far it's only happening in one project which is not an actual project I'm only doing testing recording guitar no softsynths just guitar amp mic'd. I only have to plugins the bx meter and Klanghelm vu meter. My Faderport also isn't working so whatever is affecting playback is also affecting the Faderport. I'm hoping to figure this out.

Mosvalve, transport not able to play is usually time issue- make sure your DAW is set to be slave to your sound card and there is no MIDI loop. 
 
The problem is allocated. Like I suspected, Big Fish Audio Sequence Hip Hop beat creator is responsible. Taccess, thank you for recommendation- closing window with Kontakt without deleting the synth solves the problem. This is confusing because the synth is not frozen to audio, it still playing and responds to Play/Stop, but behaves differently depending on it being opened or closed. So closing it solves the problem. Thank you again for your help. I will contakt BFA to report this.