I just bought 4gb of Crucial RAM for my late 2009 Mini (bought just last week). I put in 4g (2x2) and it doesn't boot up and I get the 1 beep. I then switched them (tried to put them in different slots) and it still didn't work. Then I finally put in 3gb (2x1) and it works. Any Ideas? Just spend $120 on RAM and it won't work will all 4 gbs!