I've been using my new Octacapture, it's pretty cool...though it doesn't seem to get as good low-latency performance as my old Firebox which seems weird. Anyhow, I've been loading older projects, which inevitably produce a major crash...a total drag.
 
But when I fire SONAR back up it doesn't see the Octacapture, and I have to reboot the whole computer to get it sussed out. What the deal with that? I checked Task Manager and it doesn't look like anything is hanging or still resident. 
 

Giving myself a little bump to see if anyone else has this issue.
 

Latest Drivers? Always the first place to start on an issue like this.

I had similar issues with an older FW interface. I also used to reboot the computer until I realized if I just unplug/re-plug the cable, the driver will reset and a full reboot wasn't required.
 
Give it a try and see if that helps.