Adding 6Gb RAM to MSI X58 mobo- really slow boot!

I added 6 more Gb RAM to a X58 mobo (total 12 Gb) running 920i7 and windows home premium and now this beast boots verrrry sloooow! Went back to normal after removing RAM (same spped, manuf,...) why is that?
thanks, Mike

I have *exactly* the same problem (also on an MSI X58)... except that I purchased all 12GB at once -- I actually found a 12GB kit! from Corsair (XMS3 1333 DDR3, 6x2GB). I am not doing any overclocking, and I have tested all the DIMMs individually.

To me, the strange part is that the step where it gets hung is the "progress bar" during Vista loading... I was thinking that a RAM capacity issue like this would be something that required a BIOS update, but because the delay is at a stage where the OS is already loading, I'm not sure... By the way, it boots perfectly fast with 8GB as well... only when I go to 10GB or more is there a problem. I know Vista boots just fine on other motherboards with more than 8GB or RAM, so it's certainly not a general problem with large RAM, but something specific to this motherboard or chipset

just wanted to confirm that the BIOS update worked great. In my case, I updated to version 1.5 (using the MSI LiveUpdate3 utility to download and flash the BIOS from within the windows environment)