The disk controller has to be configured as IDE or AHCI. Neither RAID nor SCSI are supported.
The network controller should be configured as PCnet-PCI II or PCNet-FAST III for instance. INTEL PRO or Paravirtualized Network do not work.
Converting from qemu image
It is possible to convert qemu raw image to one of the formats recognized by VirtualBox, namely vdi format.
If you are not sure if the image is a raw format, use qemu to get the information:
qemu-img info debian-hurd-original.img
To convert the image you need the VirtualBox package properly installed with a VBoxManage tool (which is part of the package). Convert image from raw to vdi:
VBoxManage convertfromraw debian-hurd-original.img debian-hurd-converted.vdi --format VDI
If QEMU with KVM is not available, VirtualBox reportedly has better performance.
IRC, freenode, #hurd, 2011-10-31:
<youpi> I don't know what virtualbox does with hardware emulation, but gnumach is awfully slow to probe things there