The issue is that blogger does not let you upload some things. I suppose flash stuff might be the same (I will have to test that). So to fix that you can get a Google Page Creator account (I got one the day they were announced) and upload there.
So, for example my script's URL is http://chris.hillman.googlepages.com/randomtext.js, because my Google page's url is http://chris.hillman.googlepages.com and the file is loaded to the root by default. Then I just specify the URL in a SCRIPT SRC attribute and BOOM! Random text joy.
It is really pretty lame but if you have a .JS file that you want to reference from Blogspot, this is one way to host it for free. Thank you a million Google, you guys ROCK!