Hi,
I've found a very interesting post here :
http://lime-technology.com/forum/index. ... ic=40683.0
According to this link, it seems to be specific to linux (Xpenology) and maybe with some virtualization stuff (VT-d option in BIOS).
Some users are reporting success with the following workaround :
add iommu=pt to the append line of your syslinux.conf file on your boot flash.
I've not tried yet...