@Oldhat: Eish G41 chipset. It doesn't officially support more than 4GB of DDR3 memory. It also doesn't support speeds greater than 1066. This is a chipset limitation. May be that Intel have upped those restrictions at some point.
Source: http://www.intel.com/content/www/us/en/chipsets/mainstream-chipsets/g41-express-chipset.html
Yes, G41 does not support either officially but most boards have an option to 'overclock' chipset to 1333 & some even 1600Mhz! The board I am using(Foxconn G41mxe) claims to support 1333 & 2 x 4gm ram. The 2 x 4Gb Axtrom ram works fine at 1066 & 2 x 2Gb Samsung ram also works fine at 1333. There are many who do have 8Gb working at 1333 with identical board - seems Axtrom just not compatible