Precision M6400 memory compatibility

Hi, I've got installed 2 x Crucial 2GB DDR3 1066MHz/PC3-8500 Laptop Memory SO-DIMM CL7 1.5V.

I 'm trying to replace them by 2 x Kingston 4GB 1333mhz DDR3 Non-ecc Cl9 - Sodimm Sr X8 (DDR3, 1.35V, CL9, FBGA, Gold)

With the new memories the Capslock keeps blinking and no boot. I've tried using slots A & D as per recommended in some post and also each one alone in A but always get blinking capslock.

Is that Kingston memory incompatible? If so, which parameters should I check for a replacement?  

Thanks,

Rodrigo.