just wondering if anyone has come across this situation.  For the longest time I was using Sonar LE along with my M-audio fast track pro interface and my Roland Fantom G6 keyboard and this is what I've come across. when everything is up and running and I look at my audio devices in sonar I can clearly see M-audio and fantom G6. I choose the m audio as my input and ouput driver and use a USB from my keyboard to the computer and it works great. Now that I've finally purchased Sonar X3 studio it no longer recognizes the m audio interface but chooses the roland fantom G6. the funny thing is, I can see the m audio in the audio driver but it wont let me select it. Now, if I disconnect the USB from my keyboard and start up the computer again a launch Sonar X3 and look at the audio drivers it shows M audio and all my audio plays just fine but as soon as the keyboard is hooked up. forget it..  have I done something wrong. will Sonar x3 studio only recognize 1 driver?????? any help would be great.  Thank you  

Could be the Preferences > Audio > Playback and Recording Driver mode is set to ASIO. The ASIO specification only allows on I/O driver to be used at a time. If SONAR sees both devices as audio interfaces and is set to ASIO driver mode, it will choose the first one it sees.
 
BTW, this forum is for older versions of SONAR. You will get faster (and maybe more accurate) responses by posting in the X series forum above this one.

Yes you can only use one ASIO driver at a time, but in this case the Keyboard probably is not using ASIO drivers. USB connectivity of this type is really jMIDI and not involved in ASIO.  
 
I can even turn my USB/ Midi devices on and off with Sonar open. Sonar will toss a warning at me and in some cases re assign any midi tracks that were pointed at the USB/ MIDI device. So this issue seems a little strange to me. 
It might be a case of Sonar being so damn picky about drivers. 
 
 
Try Re installing the drivers for the M Audio
Did the Roland come with drivers? You normally don't need them for MIDI. 
 
 

thanks very much for the quick response. When I was using SONAR LE I had the choice of picking M-audio or the Roland G6 in the preference, audio, drivers  menu from Sonar, and you could be right. it could just be Sonar being very suborn but the confusing part is if the m audio unit is turned on, and Roland keyboard is turned on the program sees both of them there. So if I choose to record a audio track, no problem hit record and away I go. If I want to record a midi track(using USB from the keyboard directly into the computer) no problem. but NOW, with Sonar X3 studio, its like you said its only going to pick one. and so what I've done is taken the midi in and out from the keyboard directly into the  back of the m audio unit and it works. (Not the way I would like it but im still learning.) Now I've got to figure out how to get Kontakt from Native instruments on board since I don't see it on the insert section of Sonar.  Thanks again for your help.

You were using a different recording mode in SONAR LE. Try using the WDM mode in X3. When it comes to recording modes, all the Cakewalk DAWs work the same.