After wasting a lot of time failing to get my usb midi keyboard to play anything at all on inserted soft synth track, I finally realised that it was a hardware issue.
 
If keyboard plugged in before win 7 64 bit is started - Sonar X3 no good
If keyboard plugged in after win 7 boots up and Sonar X3 started - that's no good either
 
so work around is
 
1) Start Windows 7 64 bit
2) Plug in USB midi keyboard
3) Start Sonar X3
 
Noted also - when I come out of Sonar X3 - it wont restart again without laptop re-boot
 
 
 

Are you plugging into a USB 3 port (also called super speed) by any chance? I've had a variety of issues with having to turn on USB 3 devices in particular orders. 

Thanks. It is actually connected to USB2 port via USB splitter.
 

Thanks. It is actually connected to USB2 port via USB splitter.
 
Don't do that. 

1. That's not the problem
2. Why?
 

Some things just don't work properly if plugged into a USB hub. It may be a Windows thing, it may be an issue with the hub, it may be an issue with the USB device plugged into the hub.

Audio interfaces and hubs are frequent problem combinations. MIDI controllers generally seem to work, but not always. I had a Novation controller a few years ago that simply would not connect properly if attached to a hub. So it's worth trying the controller plugged directly into a USB socket to see whether ot makes any difference.

As for Sonar not restarting without a reboot, it could be that Sonar isn't shutting down properly for some reason. After closing Sonar open Window's Task Manager and see if Sonar or bitbridge are listed anywhere in the running processes.

Thanks. I can confirm that giving the midi keyboard fresh USB2 port to itself, did not alter the observed behaviour. It the KB is connected before the laptop starts, X3 will recognise it and if I double click on little kb icon on the track to fetch up, say sound centre, I can play the keys with the mouse and hear stuff, but hear nothing when I press the usb KB keys. Laptops are not exactly bristling with usb ports, so it can be useful to use usb  hub. As long as I find them to work in practice just as well and only use low demand items such as mouse, memory stick etc I am happy to run with it. I would say that when u can get X3 64 bit working it seems smoother (free from stuttering) than 32 bit DAWs.
 

Yes, hubs can be useful. However, if something attached to them is not working then it's worth making sure the hub isn't the problem.

If you go into Sonar's preferences and look under the MIDI devices and controllers sections is the keyboard listed there? If so are the boxes ticked so Sonar knows to use it?

When Somar is running there is a little keyboard icon that is in the Window"s taskbar near the clock. If Sonar is receiving MIDI at all small "lights" on that should be blinking.

If the keyboard is recognised by Sonar and enabled are the keyboard's MIDI ports showing up in the list of available inputs on MIDI tracks?

Sorry if all this seems obvious, but sometimes going right back to the beginning and checking everything finds the answer.

If you have to use an USB hub make sure it is a powered one, there may not be enough power to run peripherals otherwise.  Also be aware of the fact that all USB hubs are not equal.  That is some peripherals will work with one hub but not another.  I don't know why but I do know that is true, i.e. been there done that. Also I have had hubs go bad so can you test the hub with another peripheral?

As mentioned make sure that you keyboard out and your track in MIDI channels match. That can cause the no sound from the keyboard problem.  Again been there done that!

Are you sure that the keyboard is working?  Can you test it?

It the KB is connected before the laptop starts, X3 will recognise it and if I double click on little kb icon on the track to fetch up, say sound centre, I can play the keys with the mouse and hear stuff, but hear nothing when I press the usb KB keys.
 
Well then this might be as simple as you have neglected to assign the USB keyboard as the input to the midi track. Select the keyboard as input device and OMNI mode. Make sure input echo is on. 
 
At no point have you told us what the keyboard is? Did it come with MIDI drivers? Good one do.
And it is also a good idea to always use the same port that you first connected and installed the drivers too. Otherwise windows will install and use generic drivers. And yes you always plug it in before boot up.