What you are describing sounds like the typical "drawbridge" sensation. The Swedes must have a lot of drawbridges over there because when they started doing this a bulletin was published out linning the drawbridge noise. I have had cars come back that I just installed brand new pads and rotors (factory Volvo stuff) and they were doing so bad you thought it was going to run you out of the car. The fix for it is a set of "drawbridge shims", they look just like normal shims only they appear to have a square piece cut out of the corner of them. They are available through Volvo or most of your aftermarket parts vendors. I would recommend new pads, grease, and a set of shims.

Mark