To make a long story short...
Got this M2N-E about one year ago with BIOS # unknown (I didn't record what
it came with).
I installed Vista Ultimate without a hitch and it has run fine, until...
I started beta-testing various builds of Vista SP1 RC1 and got to the point
where it was time to wipe the partition and reinstall the OS.
Sometime over the past year, I updated the BIOS to 0802

Now, when I attempt to reinstall Vista, it refuses, telling me the BIOS is
not ACPI compliant. I updated the BIOS to 1202, thinking the new one might
help, but Vista still refuses to install, citing ACPI non-compliance.
Now, I'm sitting here looking at the M2N-E box, with the "Vista Premium
Ready!" sticker on it...
Any suggestions?