I ran into the same problem* but I found a solution for me I'd like to share with you.
For me, uinstalling the driver
In the device manager I have the "CSR_BTPORT_01" entry under "Other devices". It had no driver installed and Windows added an exclamation mark to the device. Trying to find a suitable driver did not succeed (Windows Update, manual selection, etc.)
The second device was "CSR BlueCore Nanosira" under "Universal Serial Bus controllers" which had a new driver from 2011-01-13 with Driver Version 220.127.116.11 from Cambridge Silicon Radio Limited installed. Windows was claiming that the device was working properly.
You see my situation in screenshot 1.
My solution was to change the driver of "CSR BlueCore Nanosira" under "Universal Serial Bus controllers" back to the generic Bluetooth driver.
To accomplish this select "Update Driver Software" from "CSR BlueCore Nanosira" (the working device)
, then select "Browse my computer for driver software" and then "Let me pick form a list of device drivers
on my computer". In my case Windows presents the new driver from CSR ("CSR BlueCore Nanosira") and two generic drivers as you can see in screenshot 2.
I selected "Generic Bluetooth Radio" from the list and clicked OK. Then I had "Generic Bluetooth Radio" and "Microsoft Bluetooth Enumerator" back under "Bluetooth Radios" and the Bluetooth icon appeard in the taskbar again. After that I was able to use my bluetooth mouse and keyboard again (even without pairing it again).
Hope this helps for you, too!
* I accepted the update of the bluetooth driver by Windows update because I have some problems (unresponsive mouse) with Windows 7. The identical (!!!) hardware works flawlessly with Linux (in my dualboot configuration). So I was hoping for some improvement.