Thanks for the response jhung, it's with an app we've developed. It's the only Leap app we've been using so I'm not sure if it would happen with other apps.
I've had this happen with Unity sometimes, while developing the app. But I can usually just unplug the Leap Motion and plug it back in and it'll regain the connection.
I'm sorry I don't have any more exact details, but I remember on the control panel connection screen, the first "service status" is green, but everything else appears red. In many cases, unplugging and replugging doesn't fix the issue.
In one case, the app was tracking fine as a user was in the app and it suddenly stopped working. The hands stuck in place and the app appeared to be working fine otherwise.
We're plugging the Leap Motion directly into a USB 3.0 port in the PC so I don't believe bandwidth is an issue. We're using it with an Oculus Rift.
I figured exiting the control panel and reopening it was restarting the service, maybe that's not the case. I haven't tried uninstalling and reinstalling the service. The PC came with McAfee shipped on it, but we removed the antivirus after setting up the Leap Motion drivers, not sure if that could possibly have anything to do with it.