Panic during ssh/rsync (rsnapshot)

I'm using FreeBSD 5.4RC3 (this happened on 5.3R also) as an rsnapshot server. 
All this machine does, is run rsnapshot (rsync+ssh+hardlinks = snapshot disk 
backups).  I'm running 6 rsnapshot processes via cron every night at 11pm, so it 
essentially hammers the machine during that time.  About 3 out of 5 nights, my 
system dies right at the beginning with either the fatal trap (see below) or the 
panic (see below).  It seems to die just when I get about 6 rsync processes 
running.

Any ideas?

----------------
panic: sbflush_locked: cc 0 || mb 0xc3432000 || mbcnt 256
cpuid = 0
boot() called on cpu#0

----------------
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address	= 0x15
fault code		= supervisor read, page not present
instruction pointer	= 0x8:0xc077ad60
stack pointer		= 0x10:0xe898ab10
frame pointer		= 0x10:0xe898ab1c
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, def32 1, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 3100 (ssh)
trap number		= 12
panic: page fault
cpuid = 0

-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
A lost ounce of gold may be found, a lost moment of time never.
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