According to a Nikon support advisory there are a small number of Lexar 400x or 1000x compact flash memory cards that may have issues communicating with the new D4s camera. Nikon USA's service and support site has outlined how to identify the faulty cards and instructions for replacement.
CompactFlash® Memory Card check for use with Nikon D4S
Remove your CF® card from your camera.
Look for the serial number on the edge of your CF® card.
Identify if the last six part numbers (shown highlighted by the yellow X's) contain 1 of the following 2 sequences:
If your CF card's serial number contains 1 of the 2 sequences listed above, you must contact LEXAR support to replace your CF® card.
If your card does not contain either of the 2 sequences, then your card is fully compatible.
Please contact customer support to place an RMA for a replacement CF® card.
US & Canada: 1-888-747-4031
Freephone in the United Kingdom: +44 (0) 0800 013 7411