Get the 2.4.23-pre2. I forgot that I had patched my kernel with two updates, both of which are in the 2.4.23-pre2 kernel.
I had about a dozen different kernel source trees (desparate to fix my lockup problem, I tried everything) and I named them as they named the kernel (ie 2.4.22-rc2, 2.4.22-bk21, etc). Applying the patches didn't change the name of the kernel, so I forgot about doing that.
The two patches were acpi and apic updates. Again, both are included in the 2.4.23-pre2 kernel.
Remember to tell the kernel "noapic nolapic", as well as disabling APIC in the BIOS, and compiling the kernel with local apic and io apic removed.
The day after I found the fix, I flew out for an emergency job and I didn't get back until yesterday. I ran the computer all day, doing everything I possibly could to get it to lock up.
The only lockup I did have was loading Mandrake 9.2 RC2. The Mandrake load kernel has either APIC compiled in, and/or doesn't have the nolapic patch on it. Submitted it as a bug. Hopefully it gets resolved.