Congratulations mangus, and thanks for posting it.
In my news searches I missed APIC as a possible solution. I must have read APCI every time I hit it.
Interestingly I already have APIC disabled in my BIOS. I must have disabled it two years ago when getting the system going for the first time - I don't recall why. The kernel seems to ignore the BIOS. Looking back at archived syslogs it was doing this long before I started getting the X freeze problem. Some non-consecutive lines from my syslog:
Sep 8 18:34:53 domus kernel: Local APIC disabled by BIOS -- reenabling.
Sep 8 18:34:53 domus kernel: Found and enabled local APIC!
Sep 8 18:34:53 domus kernel: Using local APIC timer interrupts.
Sep 8 18:34:53 domus kernel: calibrating APIC timer ...
Sep 8 18:34:53 domus kernel: PCI: Disabling Via external APIC routing
I'll try your APIC solution next if (once) my current attempt has failed.
I'm currently disabling apm and acpi via lilo boot options: apm=off acpi=off. I probably have to wait a week or so before I know this hasn't fixed things for me.
There are lots of solutions in the news groups that have worked for some people but not others. APIC looks very promising.