I have to agree that it looks like a compatability issue, if you go to most any manufactuters site they will have a means of matching your RAM with modules of theirs which will be compatible. Most have a three step process to identify your RAM, they will ask what type of computer it is (desktop, laptop...), and for your make and model of your computer, or motherboard if it is a home build, and then show you a list of available modules which they will have tested for compatability with you computer.
You can also download Everest Home Edition, go to motherboard, then SPD to find out exactly what you have for RAM, it will tell everything you want or need to know.http://www.majorgeeks.com/download4181.html
The BIOS is the basic input / output software that is part of the motherboard, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.
I would not flash the BIOS, it dosen't look like this is your problem, and I would try clearing the CMOS before I would go to the extreme of flashing the BIOS.