Adobe Flex Builder + Air 2: Nothing Happens, nothing shows or “invocation forwarded to primary instance”

An obscure one, hard to Google. I was trying to use NativeProcess which is newly available in AIR 2.0. I wedged the AIR SDK into my Flex 3 SDK, then created a new AIR app. When I tried to run it (or debug it), nothing happened. If I tried to run it again, I got “invocation forwarded to primary instance”. This means that adl.exe is already running. You’ll have to kill that process. If I removed the reference to NativeProcess, everything ran fine. Turns out, my app.xml still referenced the AIR 1.5. Naturally, NativeProcess is not available in AIR 1.5 – but how about a damn error, Adobe? Silent failures are very AS1.

In *-app.xml

Was:

<application xmlns="http://ns.adobe.com/air/application/1.5">

Changed to:

<application xmlns="http://ns.adobe.com/air/application/2.0">