NeoLoad asks me to load some jar files at the end of my record of my Flex application. I don't know where I can find them?
When recording a Flex application NeoLoad deserializes the binary stream between the browser and the server. It will convert the binary data to an XML content.
To deserialize the objects exchanged on the network, NeoLoad needs the jar files containing those objects. You could ask the developers of your application the jar files that contain customized code for the client.
For more information, see "Adobe Flex/AMF requests" under "Design" section in NeoLoad documentation.