ipfilter 4.1.30 on Solaris 10/08

Hi,
I upgraded the original ipfilter of Solaris 10/08 rebuilding from sources of ipfilter 4.1.30
and using the contained shell to overwrite binaries.
From time to time, upone reboot of the system, after some minutes the system crashes.
After reboot again, the system runs with no apparent problem.
Look at the messages I attach below, that's why I suppose is something about ipfilter.
Maybe someone can help me to find a reason?
Gabriele.
Feb 27 15:20:02 iserver ^Mpanic[cpu1]/thread=fffffe80000c5c80:
Feb 27 15:20:02 iserver genunix: [ID 683410 kern.notice] BAD TRAP: type=e (#pf Page fault) rp=fffffe80000c59e0 addr=ffffffffc4cf9b5f
Feb 27 15:20:02 iserver unix: [ID 100000 kern.notice]
Feb 27 15:20:02 iserver unix: [ID 839527 kern.notice] sched:
Feb 27 15:20:02 iserver unix: [ID 753105 kern.notice] #pf Page fault
Feb 27 15:20:02 iserver unix: [ID 532287 kern.notice] Bad kernel fault at addr=0xffffffffc4cf9b5f
Feb 27 15:20:02 iserver unix: [ID 243837 kern.notice] pid=0, pc=0xfffffffffb8303ba, sp=0xfffffe80000c5ad8, eflags=0x10212
Feb 27 15:20:02 iserver unix: [ID 211416 kern.notice] cr0: 8005003b<pg,wp,ne,et,ts,mp,pe> cr4: 6f0<xmme,fxsr,pge,mce,pae,pse>
Feb 27 15:20:02 iserver unix: [ID 354241 kern.notice] cr2: ffffffffc4cf9b5f cr3: 10629000 cr8: c
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   rdi: ffffffffc06cf200 rsi: ffffffffc4cf9b5f rdx: fffffffffb9d5841
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   rcx: 1fffffffff73ab08  r8: fffffe80000c5a80  r9:                1
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   rax: ffffffffc06cf1b8 rbx: ffffffff860992a8 rbp: fffffe80000c5b10
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   r10: ffffffff80385e40 r11: fffffffffbced1c0 r12: bffffffffff70cb8
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   r13: ffffffff80247000 r14:            11c64 r15:       1cc59c5142
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   fsb: fffffd7ffef18a00 gsb: ffffffff86014800  ds:               43
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]    es:               43  fs:              1bb  gs:                0
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]   trp:                e err:                0 rip: fffffffffb8303ba
Feb 27 15:20:02 iserver unix: [ID 592667 kern.notice]    cs:               28 rfl:            10212 rsp: fffffe80000c5ad8
Feb 27 15:20:02 iserver unix: [ID 266532 kern.notice]    ss:               30
Feb 27 15:20:02 iserver unix: [ID 100000 kern.notice]
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c58f0 unix:real_mode_end+7201 ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c59d0 unix:trap+5e6 ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c59e0 unix:_cmntrap+140 ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5b10 unix:bcopy+a ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5b40 ipf:nat_delete+3f ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5b80 ipf:fr_natexpire+79 ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5ba0 ipf:fr_slowtimer+8f ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5be0 genunix:callout_execute+db ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5c60 genunix:taskq_thread+bc ()
Feb 27 15:20:02 iserver genunix: [ID 655072 kern.notice] fffffe80000c5c70 unix:thread_start+8 ()
Feb 27 15:20:02 iserver unix: [ID 100000 kern.notice]
Feb 27 15:20:02 iserver genunix: [ID 672855 kern.notice] syncing file systems...
Feb 27 15:20:02 iserver genunix: [ID 904073 kern.notice]  done
Feb 27 15:20:03 iserver genunix: [ID 111219 kern.notice] dumping to /dev/dsk/c1t0d0s1, offset 1932984320, content: kernel
Feb 27 15:20:11 iserver genunix: [ID 409368 kern.notice] ^M100% done: 98527 pages dumped, compression ratio 3.25,
Feb 27 15:20:11 iserver genunix: [ID 851671 kern.notice] dump succeeded
Gabriele Bulfon - Sonicle S.r.l.
Tel +39 028246016 Int. 30 - Fax +39 028243880
Via Felice Cavallotti 16 - 20089, Rozzano - Milano - ITALY
http://www.sonicle.com