Bluetooth device disappears occasionally

[wacian]

I have T61 7662-CTO
vista business

Bluetooth device disappears from fn+F5 menu at sometimes and I have to restart vista to see it again.
I have recently restored to factory settings after a clean install but at the time I had done a clean install this was resolved by switching off and then back on all wirelesses, from the switch in front of the laptop. But now this does not work too.

I have found out that this issue happens when I first turn on the laptop after a shutdown.

I have tried:
searching for new devices in device manager.
reinstalling bluetooth driver from lenovo website (when the device was recognized)

Does anybody else has the same problem? and has this thing happened to people on XP?

sorry for my bad english.

[wacian]

BTW:
I encounter "Windows Driver Foundation - User-mode driver framework host process" error in "Problem and reports" window. Also there is some events in event viewer about a device driver which has crashed.