Hmm... shouldn't be. The only object extensions are to String, Number and a few other native classes...
...but not Object or Array (which really are the only values you should ever run a for..in loop on).
But if the uninstall is broken (sorry!) you can easily uninstall by deleting any files containing the words "xjsfl" in your Flash config folder (there should only be 4 or 5) then deleting the xJSFL folder itself.
Do you think the JSON library itself is causing problems? I think in the Beta2 these are fixed - did you install the Beta2 branch or the main one?
I deleted the files as suggested but I am still having trouble . Your page http://www.xjsfl.com/support/api/data/json states that: "The JSON library is currently disabled in the core bootstrap, as it extends native objects and breaks for..in loops. I'll look into rewriting the JSON lib once the framework is officially in beta."
This appears to be the behavior I am witnessing. Do you have any suggestion how to fix?
If xJSFL is not installed, and your JSFL is still breaking, you probably want to look at other extensions which are likely the culprits. See this thread: http://xjsfl.com/forum/discussion/37/installation-problems-with-flash-cs5