While debugging, my device frequently disconnects from my PC, usually after every debug session. The device still appears in the DDMS list but the status is \"offline\". The
Connect your device through a powered USB hub. Some machines, including new apple macbooks, do not have enough power in the USB ports causing ADB to constantly disconnect.
If your device is rooted, you can connect it to adb via wifi. This is very comfortable, much more than wired USB. Of course you don't always have a rooted device.