I had mine replaced a few months back (National Windscreens) and mine creaked too. I found that when I removed the plastic panel under the windscreen wipers and refitted it, the creaking stopped. After a couple of weeks it started again. That's where I think the creak comes from - I'll be having another go at it soon as it is starting to annoy me a bit, although I blame the state of the roads too - they're really bad round Uxbridge/Denham/Amersham.