RunWebThread taking up 33% of CPU time on iPhone App

I'm making a game for the iPhone using Cocos2D. At the beginning of the game, when there are few sprites, the game runs fine, but when there are many sprites on the screen, the game gets choppy.

I've profiled the app, and RunWebThread seems to be taking up 33% of the cpu t开发者_StackOverflowime. I contact a server at the beginning of the game, but there is no Internet usage after this initial contact.

Does anybody know what this thread is doing?

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Here's your answer: http://developer.apple.com/mac/library/qa/qa2009/qa1619.html