OpenBSD 2.9 Crashing (by ipsec ?)

["Victor" <victord@paid.com>]

I got an OptiPlex Dell GX1 (Pentium II with BX chipset)
crashing sometimes. I don't get why (I have openbsd systems with yearly
uptimes).

Here is what ddb shows:

uvm fault(0xe036e0d4,0xe08d4000,0,1)->5
Kernel: page fault trap, code=0
Stopped at _fr_makefrip+0x532: movw0(%ebx),%ax

ddb> trace

   _fr_makefrip                 at 0x532
   _fr_check                    at 0x1b6
   _ip_output                   at 0x937
   _ipsp_process_done           at 0x12e
   _esp_output_cb               at 0x184
   _crypto_done                 at 0x12
   _swcr_process                at 0x1ac
   _crypto_invoke               at 0x14a
   _crypto_thread               at 0x77
   _start_crypto                at 0xb

Bad frame pointer

The system is an OpenBSD 2.9 i386

Any ideas what could be causing this? It seems like it's the IPSec part of
the code since I see "esp_output_cb". Not sure though. Anyone ever
experience this?