k3b causing kernel panic

Hi,

K3b is causing FreeBSD to panic with a recent amd64 custom kernel from 
current.  The kernel is from ~ 1 July) and does include the changes from 
r209590.  Some of the changes I made include:

options         ATA_CAM

and I have one DVD-RW installed:

# dmesg | grep 'cd[0-9]'
cd0 at ata0 bus 0 scbus0 target 0 lun 0
cd0: <ASUS DRW-1814BL 1.13> Removable CD-ROM SCSI-0 device 
cd0: 66.700MB/s transfers (UDMA4, ATAPI 12bytes, PIO 65534bytes)
cd0: Attempt to query device size failed: NOT READY, Medium not present - tray 
closed

The backtrace from the panic:

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x7fffffffca10
fault code              = supervisor write data, page not present
instruction pointer     = 0x20:0xffffffff801deffb
stack pointer           = 0x28:0xffffff80ae07ab00
frame pointer           = 0x28:0xffffff80ae07ab30
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 12 (irq14: ata0)
[ thread pid 12 tid 100039 ]
Stopped at      ata_pio_read+0x10a:     repe insw       %dx,%es:(%rdi)
db> bt
Tracing pid 12 tid 100039 td 0xffffff0002a013d0
ata_pio_read() at ata_pio_read+0x10a
ata_end_transaction() at ata_end_transaction+0x45f
ata_interrupt_locked() at ata_interrupt_locked+0x54
ata_interrupt() at ata_interrupt+0x34
intr_event_execute_handlers() at intr_event_execute_handlers+0xf9
ithread_loop() at ithread_loop+0x8e
fork_exit() at fork_exit+0x118
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff80ae07ad30, rbp = 0 ---

Is there anything I can do to assist diagnostics?

Regards,

David