I've had it many times... dozens, but not in the last 3 years or so that I remember. I typically get it in one ear. This is a real problem because this unbalanced pressure will quickly cause things to spiral out of control. Your eyes will begin to spin, vertigo and then puking soon after....
So the solution... IMMEDIATELY shoot back down. As you do it, gently try to equalize the other ear. Descend as fast as possible and as deep as it takes to stop the pain. You can then try another slow ascent. What I normally do is remove the mask and blow my nose. This seems to help a lot. Snorting seawater may help but it sounds like a good way to drown yourself.
Then just begin the ascent again, slowly, I try to open my jaw some and push my tongue down, this tends to open the tubes.. Sucking can help too....
This is reason number 5005 for why a pony bottle is not a bad idea....
I've had a few times where nothing seemed to work and I was low on air and just figured i was going to blow an ear drum,,, and so far each time.. a lot of pain and the air releases on ascent.