Nikon has updated the firmware of both the D4 and D800 professional
DSLRs. The D4 receives updates to v1.01 for both firmware A and B, while
the D800 and D800E only have B firmware v1.01. In both cases the
firmware corrects minor operational glitches, including one that could
cause the cameras to occasionally lock up. The updates can be downloaded
from Nikon's websites.
source: dpreview