It's normal for newer cards to be listed as unknown. Here's a GTX 280 that works fine:
(--) PCI:*(1:0:0) nVidia Corporation unknown chipset (0x05e1) rev 161, Mem @ 0xfd000000/24, 0xd0000000/28, 0xfa000000/25, I/O @ 0xbc00/7
(II) NVIDIA(0): NVIDIA GPU GeForce GTX 280 (GT200) at PCI:1:0:0 (GPU-0)
Attach a bug report
to your post.