Flex compiler error: "please put definition in a package" for classes that ARE in a package

This 开发者_StackOverflow中文版is with Flexbuilder 3.2, Eclipse 3.3.2.

I am moving my development environment to a new machine. Actionscript classes that compiled in the old environment now get a compile error:

A file found in a source-path must have an externally visible definition. If a definition in the file is meant to be externally visible, please put the definition in a package.

I do declare the package in these classes - I think failure to declare the package is the usual reason for this error.

To add to the mystery, many classes in this project compile without errors.

What should I check to diagnose this?

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Problem solved - I had missed out some items in the path in the environment where I was launching Eclipse.

  "C:\Program Files\Adobe\Flex Builder 3 Plug-in\sdks\3.2.0"\bin
  "C:\Program Files\Adobe\Flex Builder 3 Plug-in\sdks\3.2.0"\frameworks
  "C:\Program Files\Adobe\Flex Builder 3 Plug-in\jre"\bin
  "C:\Program Files\Adobe\Flex Builder 3 Plug-in\jre"\lib

I'm amazed anything at all worked with this much missing from my path.