I wouldn't drive the car until you have removed the pins, pads and the trapped anti-squeal spring plate. The latter holds the pins and therefore the pads in place. Can only suggest it was mis-seated when pads were last changed.
Ok thanks Richard. The pads are the originals
Did you remove pins and pads when you painted calipers though Craig?
As Dave suggests you just need to depress the spring securing plate and pins slide out. I use a broad flat blade screwdriver.
