Using a sb600 on a nikon d90?

My sb600 fires 3 quick burst of light before it fires for the picture on my d90. On my d40 i flashes only one time and that's for the shot. Is this normal for the d90 or is my settings off. I've looked through my setting and I myself can't find any thing to change.

1. Be sure red eye is disabled. This mode should never be used, especially with the SB600.

2.Is your camera set to front or rear curtain flash mode? In rear curtain, you will see two flashes, the first to meter, the second for exposing the image. In front curtain, there are two flashes, but they are so close together you only recognize it as one flash. There are times when you want to use rear curtain sync, however, you should keep it in auto mode or fill flash mode (front curtain) for most shots where there's no motion. See page 71 & 72 in your manual.

3. You could be in repeating mode. See pages 185 and 187 in your manual. This would take extra effort to get in this mode, so it is unlikely.

Sb600 on a nikon d90

- Easy-to-view LCD with 6 simple-to-understand backlit buttons
- FV lock holds flash value, enabling recomposition prior to shooting
- Accurate i-TTL flash control achieved through flash exposure monitoring control
- Ready light located beside the LCD on the back panel - highly visible even when used as a remote
- Auto zoom of 24 to 85mm, extendable to 14mm with built-in wide-flash adapter

Thanks qrk, brilliant sollution. Too easy