How old are you? have you had any back injuries before?
about 6 minths ago- i was piggy-back carrying my 8 year old to bed. i bent over at the waiste (bad idea) and it felt like somebody shot me in the back.
i too buckled to the ground and it took easily two weeks to get back to normal.
now- some of its age... some of its getting thrown off motorcycles for the last 15 years...
so ive got some strikes against me. i just have really be carefull every moment in every action.
if you have outside reasons (age/injuries/etc) it'll probably go away and i hope youve learned a lesson to 1)always be careful and 2) do some excersize to strengthen the back
if this was just out of the blue- a lightning bolt in the kidneys...
then you might have something alot worse and i'd get it checked out.
my $0.02