3 weeks ago I got my n900 back from having the usb port repaired and noticed the remove operator lock option. I was going to Australia the week after and was going to buy an ozzy sim, so I tried a payg sim to make sure it hadn't been locked in repair. the other sim worked so put my contract one back in but noticed the wifi wouldn't find my home wifi and hasn't found any wifi since even with my ozzy sim. I'm thinking this supports the sim card theory. It's getting sent off for repair on my return if it's still under warranty. Hoping they can't fix it and have to send me a shiney new one.