An issue with my nikon d90 flash?

Hi, I can't use shutter speeds of 1/250 - 1/4000 while using the flash of my camera (Nikon D90, nikkor 18-105mm), why does it happen and how can I solve it?

Why does what happen.

The standard these days is 1/200 sync speed. There are some bridge cameras, by Fuji, that will go to 1/1000, I know because I own one, but dslr cameras are generally at 1/200. Oh, you can't change it.

There are ONLY two dSLR's that can sync with shutter speeds of over 1/200th or 1/250th second.

Those are the old Canon 1D and Nikon D40.

They use CCD sensors and the sensor is turned on and off quickly. Actual shutters are limited to how fast they can sync with a flash.

Your question tells us that you have yet to take a class in photography. Do that and many of the issues you think you are having with your specific camera will be cleared up.

Above a certain speed, the focal plane shutter does not open completely at any one time. Instead, the trailing curtain is following while the leading curtain is still opening. So if the flash goes off at the higher speed there will be a section of the frame that gets no flash exposure. The electronics of the DSLR can usually detect the flash, and therefore block the faster speeds.
Back in the good old days of mechanical cameras when flashbulbs were available, there was an FP sync socket and FP bulbs. The bulbs burned more steadily, and the FP sync triggered it slightly ahead of the shutter opening. So during the high shutter speed the bulb was burning through the motion of the slit between curtains across the focal plane. A downside of this was that it did tend to waste a lot of illumination of the flashbulb burning. An x-sync bulb on a camera set to x-sync speed (which was often 1/60th sec) would give more illumination during the exposure, allowing more distance or a smaller aperture.

Actually today's flashes are smarter, and so is the camera. So buried in your D90 menu is an option to use the FP mode. With the SB600 or higher flash, you could manually set the shutter speed faster than 1/200th sec, and the flash will know to continuously burn through the motion of the shutter across the sensor plane. The setting to turn this on is in the Custom Setting Menu (pencil icon), e Bracketing/flash, e5 Auto FP.
Is there a performance price for this? Yes. Like the FP bulbs of yore, the electronic flash in this mode will be dimmer, limiting your range, or requiring a wide aperture, or making it a less effective fill flash in bright ambient light.
So far my only use of that feature has been to do the experiments that tell me I would rather leave it turned off.

A couple of you "experts" have it completely wrong. Please research this topic before commenting falsehoods.

I have a D90, and all you have to do is to set Auto FP (custom menu e5) to ON. But you have to use a speedlight that supports the Nikon CLS system. Then the camera can use shutter speeds from 1/200 to 1/4000 sec. This is pretty standard for Nikon DSLRs. Look up Auto FP. The D7000 and D3s for instance, both can go to 1/8000 in Auto FP.

This function does not work with the internal flash - only a speedlight. And the function is only available in PSAM modes.

Here is how Auto FP Sync works:

http://nikonclspracticalguide.blogspot.com/2008/03/10-auto-fp-high-speed-sync-explained.html

Essentially the flash duration is extended at speeds higher than 1/200 sec, so that the black band does not appear on the photo which would normally happen with high shutter speeds. This requires more flash power and a sophisticated flash, so the reason it is limited to external speedlights.