Flash compile error 1017

I'm getting this error when compiling a newly created application with SDK 4.1:

1017: The definition of base class Application was not found.

I can click on the SDK library path in the Flash Builder Explorer and navigate to the spark->components->开发者_如何学GoApplication object.

At least one other application linked to the same SDK compiles just fine.

For current time, the best solution will be:

1. Try to make a flex3 project, and let us know if it works.
2. Try to download any sample 4.1 project and try to compile, and let us know.
3. If you are using flex builder pack, use a plugin pack instead. Or conversely.
4. Try uninstall it completely and reinstall again.
5. Check if sdk 4.1 exist in your C:\Users\%USER%\AppData*Adobe*\ folder.

Let us know.

Thank you.