I had this problem....Not saying this will be your solution but its something to check.
I found that it was corrosion behind the NSR ABS ring, which caused it to be pushed out, and wear off the graphite ring that the sensor uses to take its readings. (Can't personally verify this, this is how it was explained to me) it was an independent renault specialist that finally diagnosed the problem for me, cut out the corrosion and replaced the ring with a one off a laguna (which he just happened to have kicking around).
Initially he diagnosed it to a snapped clock spring in the steering column (this was damaged by a different garage when my exhaust manifold was replaced)