6.2 and ATM (NATM) freezes

I've here a 6.2 box, custom kernel (added NATM-Support, kicked things
like RAID-Controllers); ATM-Stuff as (Card is a ProSUM STM1):

device atm
device en
device patm #IDT77252 cards (ProATM and IDT)
device utopia #ATM PHY driver
options NATM #native ATM

options LIBMBPOOL #needed by patm, iatm

Hardware is an opteron based system, dual-core - anyway not amd64 but
i386 Version installed. make.conf nearly untampered but
CPUTYPE?=opteron

System freezes (completely) after an "ifconfig" on the patm0-interface.
atest# ifconfig patm0 192.168.1.1

(thats it, system dead; does not respond to anything - not even ACPI-
Events like pressing the power-Button).


Various System-Output:
%uname -a
FreeBSD atest.linznet.at 6.2-RELEASE-p4 FreeBSD 6.2-RELEASE-p4 #0: ...

%ifconfig
patm0: flags=800<SIMPLEX> mtu 9180
media: ATM Multi-mode/155MBit
status: active

%sysctl -a | grep atm
ifatm 1 1K - 1 64
hw.atm.patm0.lbuf_max: 1024
hw.atm.patm0.max_txmaps: 1024
hw.atm.patm0.phy_loopback: 0
hw.atm.patm0.phy_type: 1
hw.atm.patm0.phy_name: Suni/Lite (PMC-5346)
hw.atm.patm0.phy_state: 33
hw.atm.patm0.phy_carrier: 1
dev.patm.0.%desc: NICStAR (77222/77252) ATM adapter
dev.patm.0.%driver: patm
dev.patm.0.%location: slot=8 function=0
dev.patm.0.%pnpinfo: vendor=0x111d device=0x0003 subvendor=0x0000 subdevice=0x0000 class=0x020300
dev.patm.0.%parent: pci2
%

%pciconf -vl
[...]
patm0@pci2:8:0: class=0x020300 card=0x00000000 chip=0x0003111d rev=0x05 hdr=0x00
vendor = 'Integrated Device Technology Inc.'
device = 'IDT77222/252 MICRO ABR SAR PCI ATM Controller'
class = network
subclass = ATM
[...]

%dmesg
[...]
patm0: <NICStAR (77222/77252) ATM adapter> port 0xe800-0xe8ff mem 0xfcfff000-0xfcffffff,0xfac00000-0xfaffffff irq 16 at device 8.0 on pci2
patm0: carrier detected
patm0: ProATM 155 interface; idt77252 Rev. F; Suni/Lite (PMC-5346) PHY
patm0: 512K x 32 SRAM; 16384 connections
bus_dmamem_alloc failed to align memory properly.
patm0: [GIANT-LOCKED]
[...]

The "bus_dmamem_alloc" message seems to belong to the patm-driver. should
one seriously care about it?

Any Hints?
Clemens.
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