I have an Alienware M11x notebook computer. Recently I purchased a Sony bluetooth headset. I had not previously used any bluetooth devices on the computer.
I set the laptop to discover devices and set the headset to be discoverable. After pairing the headset to my laptop, I opened my music folder and started listening. After hearing music for about 60 seconds, the headset went silent and the music starting coming out of the speakers instead. I then tried to 'restart' the laptop's bluetooth receiver but there was no way to do it. It was even missing from Device Manager. Finally, I closed the display and let it go to sleep. When I resumed again, the bluetooth was back. I was again able to listen to music but, after another minute or two, the device again disappeared. I even called Alienware support. He upgraded the BIOS and reinstalled the bluetooth driver, but it would never work. This was because he never had me actually shut off the computer. In other words, once the bluetooth device was gone, the only way to get it back was to sleep or shut down (power off, not just reboot) the machine.
After these steps failed to resolve the problem, the technician set up an appointment for me to get the bluetooth adapter replaced. This went very smoothly (great on-site support), but when I got home, the problem was still happening even with a new bluetooth module.
To make a long story not much longer, I was able to fix the problem. It turned out that it was the power options for the Dell Wireless 365 Bluetooth Module. I unchecked the checkbox labeled 'Allow the computer to turn off this device to save power' and the problem was solved.
So, step by step, here's how to fix the problem in Windows 7:
1. Click Start
2. In the search box, type 'Device Manager'
3. In the results window above, click Device Manager,
4. Expand the Bluetooth Radios node in Device Manager (remember, you have to do this when the bluetooth device is there. If it is not shown, then it has already been shut off and you'll need to shut off or sleep the laptop and resume again to get the device back again).
5. Right-click on the Dell Wireless 365 entry and choose 'properties'.
5. Click on the 'Power Management' tab and uncheck the 'Allow the computer to turn off this device to save power' and click OK.
Problem solved. I hope this helps others.