random panics: vm_phys_free_pages: page 0xc22c72a0 has unexpected order 10

I  am  getting random panics with 7.0-CURRENT i386, a couple of
examples  of  what has been triggering them is extracting ports
tree via portsnap and compiling ports.

Unread portion of the kernel message buffer:
panic: vm_phys_free_pages: page 0xc22c72a0 has unexpected order 10
cpuid = 0
KDB: enter: panic
Uptime: 1h35m53s
Physical memory: 1011 MB
Dumping 167 MB: 152 136 120 104 88 72 56 40 24 8

#0  doadump () at pcpu.h:195
195     pcpu.h: No such file or directory.
     in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:195
#1  0xc074d98e in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2  0xc074dc4b in panic (fmt=Variable "fmt" is not available.) at 
 /usr/src/sys/kern/kern_shutdown.c:563
#3  0xc0969ace in vm_phys_free_pages (m=0xc22c72a0, order=0)
 at /usr/src/sys/vm/vm_phys.c:419
#4  0xc096443e in vm_page_free_toq (m=0xc22c72a0)
 at /usr/src/sys/vm/vm_page.c:1308
#5  0xc0964526 in vm_page_free_zero (m=0xc22c72a0)
 at /usr/src/sys/vm/vm_page.c:511
#6  0xc09fe043 in pmap_remove_pages (pmap=0xc6c00344)
 at /usr/src/sys/i386/i386/pmap.c:1142
#7  0xc095d64c in vmspace_exit (td=0xc75bc000) at /usr/src/sys/vm/vm_map.c:395
#8  0xc072eaeb in exit1 (td=0xc75bc000, rv=0)
 at /usr/src/sys/kern/kern_exit.c:294
#9  0xc072f8ad in sys_exit (td=Could not find the frame base for "sys_exit".) 
 at /usr/src/sys/kern/kern_exit.c:98
#10 0xc0a025b3 in syscall (frame=0xe678bd38)
 at /usr/src/sys/i386/i386/trap.c:1008
#11 0xc09e8850 in Xint0x80_syscall ()
 at /usr/src/sys/i386/i386/exception.s:196
#12 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)

Any help would be greatly appreciated.

Regards

Brad