I didn't get this error while testing it.
This is not related to the exit problem, but the Bluetooth functions are only supported on devices with Microsoft Bluetooth stack. You should use an ErrorLabel that catches the error that will be raised on line 34:
If hardware.BluetoothMode = 0 Then mnuBlueOff.Checked = true Else mnuBlueOn.Checked = true
In order to find the problem I recommend you to temporary remove the GotFocus / LostFocus subs (maybe there is a recursive call in these methods) and disable the timer and see if it helps.
If your device is low on memory then opening other applications may also cause all kinds of problems to your application.