Severity and Description    Path    Resource    Location    Creation Time    Id
An internal build error has occurred. Right-click for more information.        ****** Unknown

解决方法很简单，按如下步骤：

Help > Product Details. 点击 Configuration Details 按钮, 点击 View Error Log 按钮.

一般地，我们会找到这样的错误：

java.io.FileNotFoundException: D:\projects\google\MyProject.swf (The process cannot access the file because it is being used by another process)

at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at com.adobe.flexbuilder.multisdk.compiler.internal.ASApplicationBuilder$MyBuilder.mybuild(ASApplicationBuilder.java:282)
at com.adobe.flexbuilder.multisdk.compiler.internal.ASApplicationBuilder.build(ASApplicationBuilder.java:122)
at com.adobe.flexbuilder.multisdk.compiler.internal.ASBuilder.build(ASBuilder.java:139)
at com.adobe.flexbuilder.multisdk.compiler.internal.ASItemBuilder.build(ASItemBuilder.java:73)
at com.adobe.flexbuilder.project.compiler.internal.FlexProjectBuilder.buildItem(Unknown Source)
at com.adobe.flexbuilder.project.compiler.internal.FlexProjectBuilder.build(Unknown Source)
at com.adobe.flexbuilder.project.compiler.internal.FlexIncrementalBuilder.build(Unknown Source)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:624)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:166)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:197)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:246)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:249)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:302)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:334)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:137)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:235)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

原因就是表黑的那个文件被FlashPlayer.exe进程打开但没有关闭，因此Flex编译好的新文件无法覆盖这个文件。解决方法非常容易，打开Taskmgr，找到FlashPlayer.exe干掉就好了：）

http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4

最近在用Flex Builder3做项目，感觉Flex Builder仍然拿是最好的ActionScript3编辑器。