I have a USB Midisport 4x4 box, interfacing a computer and Roland keyboard.  I recorded a midi bass track with Sonar X1. 
 
There are four USB inputs on my computer.  I moved the Midisport USB cord to a different USB input.   Now my bass track will not play.  I have tried putting the the cord back in it's original slot, but it won't find the same port.  It seems the USB port numbers in the computer change on their own.
 
Is there a way to zero out port USB tags, for a midi track?   Or rename the port number?
 
thanks
wadrum

First just so you know, this is the old forum for 8.5 etc. But your problem is not DAW specific any how. 
 
It is advisable to always plug a USB interface into the same port to avoid loosing the drivers. 
You should get your device back by restarting. 
Sonar always complains when it looses a device that was used in a project, Example I forget to turn on my Yamaha drums. I just turn them on and Sonar pops up a thank box and asked if it's ok to connect. I would think the Midi sport would behave the same. Are you using Windows 7?