It might take more than a week to get repaired/replaced. I took mine in to a Carphone Warehouse (one which was listed as a Nokia Service Centre (or something like that) on Nokia's site) because I didn't want to wait in for it to be picked up and it's been two weeks now, but I'm not sure how long it took for them to send it on to Nokia, I took it in on a Wednesday, then according to the online tracker it was sent to Nokia on Saturday, then the following Saturday I got an automated call telling me it had been sent to Nokia and the online tracker had been updated to that Saturday. So I'm still waiting, and in the meantime I've bought a second N900 (second hand) to keep me going.

On the plus side, there have been many reports of the N900 simply being swapped for a new one when they have been sent for repair with this fault, so hopefully I'll have a new one when I get it back.