I've had two expierences between mid-November '09 to now.
It usually happens while I'm asleep.. the first time I'd woken to a throbbing headache that felt like my head was going to explode. I stood up, then the pains got worse; my head throbbed harder and I could hear some sort of pumping noise in my head. I felt dizzy, and my shoulders hurt so much I could hardly move my arms. My lips turned to a purplish-blue colour and was having cold-sweats.. So I sat down and took deep breaths, and they slowly went away in about 10 minutes.
The second experience was similar, while I was asleep, only the pains weren't as bad.
Answers? Would be appreciated.