It seems that the SB-900's have a built in function to turn off if they over-heat and apparently they heat up PRETTY fast! There have been quite a few complains on Dpreview regarding this, anybody have any experience?
I had this happen once, during a wedding in the summer. I have heard various conditions help contribute to this, such as hot temperatures outside, rapid flash firing, possible types of batteries used, etc.
I know for me when it happened it was hot outside (93 degrees and extremely humid), and I was flashing away, so the flash shutoff for about a minute or so, but it seemed like an eternity. It seems to be a safety feature for this flash, even though most look at it as PITA.
I agree it's a good safety feature.
I rather not able to use the flash for a few minutes, than able to use it for just a few more minutes and then never again.