Foam as the bottles age....

I have two batches of beer (well, the remnants, less than two sixes of each) made early this year, both well-hopped pale ale styles, both made sequentially, the second made on the yeast cake of the first. Until recently, I would say that both batches had a nice head, good lacing. Then, within the last month, they have -both- started to foam up and out of the glass, no matter how much I chill or how carefully I pour. A regular 12 oz. longneck will produce foam that will come up out of an Imperial pint glass. This is a thick foam that can practically be cut with a knife. Beer still tastes OK, and I'm certain that the cleanliness of my glassware is not an issue here. I prime with 5 oz. dextrose (corn sugar), and out of maybe 60 batches of beer made in the two years I've been brewing, and a wide variety of styles, this has never happened. Any thoughts, ideas speculations?

If it's got a sour note to it, it's probably lacto. If it still tastes ok, it's probably a gusher infection. Drink it quicker, if that's the case. It'll get worse.

+1 Both types of bacteria can consume the complex residual sugars and cause foaming. And they just keep getting worse.

Well, live and learn. And it makes sense in this case, since the two batches have the same yeast cake in common......