Device hangs after USB cable removed

After I plugged my 540 into my laptop for charging or a sync, I dismount the device and then disconnect the USB cable. The device then powers up, only it gets stuck with the message "loading courses, workouts and locations". Normally this "loading" message appears for a few seconds before the device is ready, here it can last for 20 minutes so I give it a hard reset.

I can resolve this with a hard reset each time but it seems to be a recurrent problem, a software bug. Is there an explanation or a fix please?