Interestingly I've had several BSODs yesterday while I had UR open. The BSODs were unrelated to UR.
The clicking sound stopped playing. The Windows sound used still worked, it still played in Windows Explorer but it did not play in UR.
I even used the compact&repait feature of UR to make sure the database open at the time of BSODs was okay, but the clicking sound did not return.
Only today, after changing icons of some items, the clicking sound came back.
go figure...
k