My Nexus 7 used to work fine in Windows 7 64bit, but now all of sudden when I connect it, it shows me the new device screen, it shows in Eclipse/ADB as Nexus 7 with Android 4.3 (correct), and then disappears a second or few later, with Device Disconnected in ADB log.
ADB then reports it as 'Offline' with OS unknown.
I have tried three different USB cabled, different USB ports, and on my Mac (not my main dev device though), the device works well. This is really frustrating. I tried setting the connection to PTP and Media Device. Both don't help.
Try disabling and re-enabling usb-debugging.
Also try this:
1: uninstall the driver in the device manager with option "delete the driver software for this device"
reconnect the Nexus tablet
2: let windows install a default driver which will be inadequate
3: uninstall again the device in the device manager with the option "delete the driver software for this device"
4: let windows try to find the driver, this process will fail
5: go back to the device manager and right click the failed device and update driver
6: choose the driver location in the android sdk directory (android/extra/google/usb_driver)