Windows 7: Windows 7 Ultimate 64-bit doesn't support 4GB RAM?

Are you sure about that board number? The 5N32 is 32-bit so will not recognize more than about 3.3gb anyway.

EDIT: I stand corrected....it will take up to 8gb RAM according to ASUS but the RAM sticks must be of specific makes/types.

The number 32 relates to the amount of PCI-Express lanes.

Yes, I did go back and edit my post, sorry about that. I've been combing the internet on this subject and so far have come up with lots of theories but no firm solution for you guys.

I have 6gigs of RAM and Windows 7 installed flawlessly.

You must have cheap hardware.

It's not really fair to say. Because his system might run other operating systems flawlessly. This is an issue specific to Windows 7.

was previousely using vista 64 which ran fine.

Ran windows 7 32bit fine as well with 4gigs. just 64 bit that has this problem.

I dont seem to have or cant find a max memmory setting in my bios.

I suggest running a memory diagnostic like MemTest86+:

Memtest86+ - Advanced Memory Diagnostic Tool

It's OS independent. I don't know whether the 64 bit version of Windows 7 has more trouble booting with glitchy RAM than the 32 bit version.

I'm running Home Premium X64 with 12GB of RAM. (The maximum it supports is 16GB; it goes to 192GB with Pro.)

I'm having the same issue Simon, it's not your hardware. Well, it is your hardware, but specifically, it's the fact that Windows 7 can't support your hardware yet. It seems to be an issue with owners of certain Asus mobos with Athlon processors.
I am running:
Asus M2V-MX mobo
Athlon X2 6000+
2x2048MB Kingston RAM

Before Windows 7 I was running XP Pro-64 with no problems. Then when I tried to run a clean install of Windows 7 everything froze until I took out 2GB of ram.
It's been mentioned in several forums. This thread seems to have a BIOS tweak that may help some people, but it's not an option on mine.
Anyone have issue with installing windows 7 x64 with 4GB ram

Unfortunately, that stick of RAM might have to sit in your drawer until Microsoft comes up with a patch.

Does this issue just occur on the Ultimate version of Windows 7?

Bottom line, it is not Windows 7 Ultimate problem.
That is so obvious that it could not possible that Microsoft let that bug out.

I would think the problem most likely is the board or bios. Make sure the setting on the board is correct and the bios is up to date.

I installed Windows 7 x64 Ultimate version on a Asus motherboard. Later I replaced the Core 2 CPU with the Quad and got into trouble, machine won't boot. I put back the old CPU, got to the web downloaded the latest Bios and believe or not I had to use a floppy drive to update the bios. Once updated, put in the Quad, problem solved.

The CD supposed contain both 32bit and 64bit version. Put back 4G RAM, install the 32bit version. It will use 3G RAM. If you have installation with that too, you know your problem is your motherboard, Bios or possible you damaged your RAM or did not seat the RAM in the socket properly (Swap the RAM and see if you have damage the RAM strips).