The first thing I noticed was that a select for .2 seconds seemed to
hang in a python script I was working on that time. I didn't believe it
so I tried some other things including "sleep 1", "usleep 1", stracing
them and it all came down to one conclusion

	the clock has stopped

/proc/interrupts confirmed that the clock has stopped:

$ cat /proc/interrupts 
           CPU0       
  0:    7745428          XT-PIC  timer
  1:          2          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  8:          1          XT-PIC  rtc
  9:          0          XT-PIC  via82cxxx, usb-uhci
 11:      12106          XT-PIC  usb-uhci, usb-uhci, eth0
 12:      12079          XT-PIC  eth1
 14:       8582          XT-PIC  ide0
 15:       8623          XT-PIC  ide1
NMI:          0 
LOC:          0 
ERR:          0
MIS:          0
$ cat /proc/interrupts 
           CPU0       
  0:    7745428          XT-PIC  timer
  1:          2          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  8:          1          XT-PIC  rtc
  9:          0          XT-PIC  via82cxxx, usb-uhci
 11:      12116          XT-PIC  usb-uhci, usb-uhci, eth0
 12:      12079          XT-PIC  eth1
 14:       8582          XT-PIC  ide0
 15:       8623          XT-PIC  ide1

notice that network irqs are taking place for eth0 but no timer irqs.

halt, reboot (-f) etc didn't work because they all wanted to sleep. I
had to power cycle. Now HZ is ok (1000) again.  HZ has been patched but
that's an unlikely cause (patch attached in case you wonder).

Hardware: VIA CL6000

At the time this happened I was also playing with /dev/ttyS3 lines on
the mobo (static discharge?)

-- 
Frank