Flex编译错误 - Whitespace is not allowed before an XML Processing Instruction

环境：FlashBuilder4.0,Windows7

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问题：Whitespace is not allowed before an XML Processing Instruction (<? ... ?>)

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解决方案：自己粗心大意，把<?xml version="1.0" encoding="utf-8"?>前面多敲了空行，所以需要检查一下MXML格式。