Hello
I had a very similar problem with my 03 clio. Every time I accelerated through a certain rev, it would die. (Hence the speed or gear I was in did'nt matter). I took it back to Renault 3 times while it was still under warrenty but they did jack s**t to fix the problem, claiming their diagnostic computers had registered no faults. Eventually a chap at the garage near me managed to find the problem. He found a cable (to do with the ignition system) chaffing on the edge of the engine. So every time the car vibrated at a certain point the cable made contact with the engine, causing an EARTH so you would lose power for a split second, causing the car to almost lurch. I'm not sure which cable it was but I'd check all cable looms you can get access to.
hope this helps a little
mikey s
June 2007