#2. "RE: SB-900 Won't Unlock from D300" In response to Reply # 0
I am unsure if the following suggestion will help but I had the opposite problem. The SB-900 fell out of the D300's hotshoe although it was in the locked position. I put the 900 back into the hotshoe and locked it and again it would slide back out. I took a pair of long nose pliers and ever so slightly bent the metal prongs down on the hotshoe. It worked and now the SB-900 properly locks/unlocks. Perhaps you can pry the prongs up a bit to let the 900 slide back out?