Latitude e5440 RAM problem!

Hi folks, I've recently bought and installed a brand new 8Gb Kingston RAM memory (KCP316SD8/8), it should be compatible with my Dell Laptop (e5440) but after installing, the laptop just won't start. Power button will light  and fan will turn, coming to a stop in a split second. I've tried different configurations: inserting the memory stick in a different slot, with and without the default 4 Gb RAM. Nothing seems to work, it won't start anyhow if the memory stick is in :(

Anyone else experienced this? Any ideas?

Miguel