Nikon has released a firmware update for the Nikon SB-900 flash.  The following improvements have been made in version 5.02

• With uninterrupted shooting with the SB-900 set to i-TTL mode, images captured just before the flash ceased firing were sometimes overexposed. This issue has been resolved. By resolving this issue, metering precision has been further increased and the number of times the flash fires has also been increased.
• When the SB-900, set to TTL auto flash mode, is used with a camera supporting the Nikon Creative Lighting System (CLS), flash mode automatically changes to A mode according to camera communication status. That flash mode was previously maintained, but it has been modified so that TTL auto flash mode is restored once the SB-900 again recognizes the camera as a CLS-compatible camera.

Additional details and downloads can be found via the following links to Nikon:

SB-900 Firmware Update 5.02 – Windows

SB-900 Firmware Update 5.02 – Macintosh