I just updated my AIR runtime to 3.0 and noticed that my AIR application doesn't work anymore (my logfile reports an Uncaught Error #1508). So I tried to debug it with Flash Builder, but when I run it there, everything works just fine. So I uninstalled the AIR runtime completely but noticed that I can execute my AIR app within Flash Builder still just fine. So the AIR runtime used within Flash Builder seems to be a different one than the systemwide installed AIR runtime. How Do I chose within Flash Builder which runtime to use and how do I update this runtime?
When you use Flash Builder, it uses the copy of the AIR SDK that is inside the Flex SDK. This has a complete AIR runtime that is used for debugging. You can choose which AIR runtime to use by switching to a Flex SDK that has a different version of AIR. You can update any Flex SDK by copying the new AIR SDK into it, replacing any existing AIR files. (On a Mac there are some gotcha's here because copied folders are replaced not combined.)