[FreeBSD 5.3-STABLE] The alternate system clock has died ...

When typing

systat -vmstat

on console of my workstation I get this message:
The alternate system clock has died. Reverting to ''pigs'' display.

I recognized this earlier in FreeBSD 5.3 as I utilized 5.3-BETA. This "error"
occurs not everytime I use this command, but it seems to signal some problems.

I reported earlier herein about weird and curious freezings of my SMP box
(ASUS CUR-DLS, Server Works/RCC LE 3.0 chipset, SCSI equipment (no ATA), two
PIII 866Mhz, 2x 512 MB RAM). What does this above mentioned 'error' mean, is this
a possible cause of a SMP fault?

Thanks a lot,
Oliver