Nikon Speedlight SB-900

I take my flash off and on the camera all the time but, this time it is stuck. Is their a way to release it?.

I agree with all Nigel´s comments on the SB900 and especially what he calls its "Achilles heel". It almost requires a "Help" button and menu as you find on computer programmes as remembering all the functions requires membership to Mensa! Like a lot of equipment we don´t need or use all the functions so just remembering some basics covers most eventualities.