Could not resolve <esri:Extent> to a component implementation.

[BarraLoubna]

Hello,

This is the first time I use flex in flash builder and I just tested the sample below:

http://help.arcgis.com/en/webapi/flex/samples/index.html#/World_Topographic_Map/01nq00000044000000/

But I got an error:
Could not resolve <esri: Extent> to a component implementation.
Someone already had the same error, what to do?

Enclosed a picture of the interface work.

[BarraLoubna]

I found a solution:

http://support.esri.com/es/knowledgebase/techarticles/detail/35257