I have a W510 complete with a Thinkpad bluetooth mouse. I have gone through the process of linking them both and it works for a short while, then the connection fails and I have to go through the process again. I have recently had my Windows Ultimate upgraded to 64bit.
I had a similar problem at one time. My bluetooth would just stop working for some reason. However, I never had to go through the process of pairing it again. I just had to turn the mouse off and back on to get it to work again. After going through the steps listed below I haven't had a problem.
Go to device manager (under my computer)
Open 'Bluetooth radios'
Right click on 'bluetooth module' (NOT enumerator)
Go to 'power management' tab
Uncheck the 'allow computer to shut device off to save power' box