Few months ago I reported that there is an issue (error message) when using Nikon D4 cameras with any of the SanDisk Extreme Pro CF 160MB/s and Sony XQD S memory cards at the same time. In a recent response to a reader’s email, Nikon confirmed that they are working on a solution (most likely a firmware update). In the mean time they suggested using only a CF card (without XQD in the other slot) or using a CF card with a lower write speed, such as the 90MB/s SanDisk versions (with XQD card in the other slot).
I have the feeling that the new D4 firmware update will be announced together with the D4s in February.
