this happened to me last week Kevin....while i was sitting....all of a sudden..
i had to crawl to get upstairs to bed...crying the whole way..
our medical service sent a doctor who shot me up with voltorin (don't know what that's called in the US, maybe the same thing)..
but besides that he said i should take heavy doses of ibuprofen.....much safer than what people usually take for back pain...
he said it would take about a week for the anti-imflammatory effects to take hold....but actually after about 3 days it really really really improved...
but for a while there, all i could do was lie down or stand up...sitting was out of the question....
i hope you're feeling better soon...