The 2 usb devices mentioned ,Arturia Beatstep and AlphaTrack, do not play together well in Platinum. And...
Sonar tells me that there is not enough memory for the Beatstep, although I have 12 gigs of it,under the hood.
I have tried changing the usb ports for both devices, but no luck!
Any suggestions?
 

Here is a link to specs: https://www.frontierdesign.com/Products/AlphaTrack/Specifications
 
This device requires USB 2 or 1.1, from the looks of it, and while you may have switched ports could they both have been USB 2?
 
Bob Bone