Why isn't frozen lemonade frozen?

Frozen orange juice gets downright solid. So does frozen pineapple juice, grape juice, and every other juice I’ve tasted. So why doesn’t my frozen lemonade solidify? I ran a search, but turned up nothing.

I think it has too much sugar.

Cecil notices this too, but doesn’t explain why: http://www.straightdope.com/classics/a2_040a.html

Though he does say that apple and grape juice act like lemonade in this regard, too.

WAG: lemon juice concentrate requires lower temps in order to freeze because it is more acidic.

Whoa, wait. Cecil says the exact opposite of that (OJ has a “mushy intermediate” but the others act like water… liquid, or frozen solid).

Are we sure the OP is really true? I think frozen lemonade freezes solid as ice, unless it’s specially produced as a soft-serve beverage.

I have never seen canned frozen lemonade get anywhere close to solid. Not in the freezer in the store, not in any freezer I have owned. I have no idea how acidity would affect freezing point. Is lemonade saltier than orange juice?