I just started playing with the flex sdk, and noted two things when building the samples.
First if you are on Feisty and you don't have the sun jdk installed, you will get segmentation faults. Downloading the java sdk from the sun site, installing it, and modifying the path so that the newly downloaded jdk version runs should fix the issue.
Second when building the flex sdk samples in OS X in a background terminal leads to focus issues. In my case, I was reading in a web browser, and all of a sudden the browser would lose focus. The focus would go to flex2.tools.Compiler.
Just some items of note.