Yahoo! Pipes breaks for Flash if you customize your pipe URLs
I love Yahoo! Pipes. It has saved my butt on several occasions when I've needed to transform feeds. However, I think I broke it (for myself, at least) by customizing the URL for my pipes.
When you do that, you lose the ability to refer to your pipes using the yahooapis.com domain and thus you cannot load your data from Flash. There doesn't seem to be a way to revert to non-customized URLs either once you've made the switch.
The problem is that the yahooapis.com domain contains the necessary crossdomain.xml file but yahoo.com doesn't. Normally, what you do is replace the yahoo.com URL you get for your pipe with yahooapis.com to use it in Flash (why not just give the yahooapis.com URL as default and save Flash developers a bunch of confusion?)
Once you've customized your domain, however, that substitution results in a 404.
Here's hoping the Yahoo! Pipes team fixes this soon.
In the meanwhile, I guess my only recourse is to set up a new Yahoo! account and use that for my pipe.