panic: spin lock nv0 not in order list

with a fairly resent current im now getting:
...
nv0: <NVIDIA nForce MCP2 Networking Adapter> port 0xd400-0xd407 mem 
0xdd087000-0xdd087fff irq 11 at device 4.0 on pci0
panic: spin lock nv0 not in order list
at line 1207 in file /r+d/5.2/src/sys/kern/subr_witness.c
cpuid = 0; 
Debugger("panic")
Stopped at      Debugger+0x55:  xchgl   %ebx,in_Debugger.0
db> tr
Debugger(c0891bac,0,4b7,c0894fd6,100) at Debugger+0x55
__panic(c0894fd6,4b7,c089565a,c616b1d0,0) at __panic+0x172
enroll(c616b1d0,c08ec544,c0894fd6,1d9,1) at enroll+0x21b
witness_init(c616dae0,24,0,c6158100,c0c21b34) at witness_init+0x198
mtx_init(c616dae0,c616b1d0,0,1,c06695e0) at mtx_init+0x10e
nv_attach(c6158100,c614504c,c08bc450,0,c6158200) at nv_attach+0x81
device_probe_and_attach(c6158100,0,c0c21c20,c05968fc,c6158d00) at 
device_probe_and_attach+0xa9
bus_generic_attach(c6158d00,0,5c,c0c21c10,0) at bus_generic_attach+0x28
pci_attach(c6158d00,c60e504c,c08bc450,0,c21ce800) at pci_attach+0xac
device_probe_and_attach(c6158d00,c21ce800,c0c21c84,c0828f0a,c21ce700) at 
device_probe_and_attach+0xa9
bus_generic_attach(c21ce700,c08ad56b,0,c0c21c74,0) at bus_generic_attach+0x28
legacy_pcib_attach(c21ce700,c613e04c,c08bc450,c21b8ac0,c21ce800) at 
legacy_pcib_attach+0x8a
device_probe_and_attach(c21ce700,c21ce800,c0c21ce0,c0812abb,c21ce800) at 
device_probe_and_attach+0xa9
bus_generic_attach(c21ce800,c0c21ce0,c0665adb,c092d0e8,c21ce800) at 
bus_generic_attach+0x28
legacy_attach(c21ce800,c613a84c,c08bc450,0,c0930ca0) at legacy_attach+0x1b
device_probe_and_attach(c21ce800,c21ce880,c0c21d2c,c081af3c,c21ce880) at 
device_probe_and_attach+0xa9
bus_generic_attach(c21ce880,c21ce880,c0c21d58,c06612b9,c21ce880) at 
bus_generic_attach+0x28
nexus_attach(c21ce880,c613504c,c08bc450,0,c21c0960) at nexus_attach+0x1c
device_probe_and_attach(c21ce880,c21c0960,c0c21d7c,c08087d9,c21cee00) at 
device_probe_and_attach+0xa9
root_bus_configure(c21cee00,c08af257,0,c0c21d98,c061ec85) at 
root_bus_configure+0x28
configure(0,c1ec00,c1e000,c1ec00,c1e000) at configure+0x29
mi_startup() at mi_startup+0xb5
begin() at begin+0x2c