had a similar problem to this.
So I tried burning at 1x. Worked only some times then.
Cured it by flashing burner (Panasonic LF-D310) firmware back one version (from version A128 to A127).
Burns fine everytime now. Aparently in the first 10 - 20 secs of a burn the drives burn speed is 'callibrated'. Failure at this operation was occuring.