The problem is that three use a different type of sim, if you look at the chip on a three sim and compare it to any other carriers chip you'll see a difference in size. I think it's like if your three sim is over 6 years old it'll work in the n900 and if it's newer, well... this is the result. I'm hoping Nokia will bring out a fix as im currently stuck with my three sim in my 5800 and i' using some junk tmobile one in the n900.