Did you get this figured out? I have just switched over the Flash Builder from Flex Builder where I had the setup working just fine. I have verified the settings in each IDE are identical to get the CF debugging working when my remote cfc's are called from Flash content. I've confirmed/tested that the RDS server is running, and connects fine. However, when I put a breakpoint in the CF content which gets called, it doesn't hit it.
It's pathetic how little documentation/information there is on topics like this when we're dealing with two Adobe products that are supposed to work together so nicely.
I got on line with tech support to get them to show me how to use it. The guy hardly knew anything about it himself. From the coldfusion group and was the guy who was supposed to know. I screen shared with him and every time we tried debugging from flex it would just stop. Seems that if something goes wrong in a coldfusion library, the debugger just stops and so it is something upsteam of your break point. Of course there is nothing to show you that, but it became clear. The guy didn't have any better idea than I did what was going on. I figured that out.
If you check the docs about CF and flex, their recommendation is write it all as a CF app. debug it and then hook flex to it. Pure garbage. Anybody hear of DRY. I have dumped ever using CF on the back end. It is not an oop language. It is a tag based language for markup pages with quasi script and its ORM is so inflexible its a joke.
Went back to ruby on rails and rubyamf for my backend to flex apps (with Mate as MVC framework) and I could not be happier. Never had such an unpleasant develpment experience than working with Coldfusion as the backend to a flex app. Good luck.
I would have to agree, doing Flex on top of CF 9 ORM has not been fun, and is extremely hard to debug. I pretty much have to go over to using my unit tests as a testing platform for any remoting code, but it is only a cludge and not always successful. Right now my application is working in Firefox but not IE and I'm totally frustrated trying to figure out why. It boggles me that they can't get their own languages working seemlessly together and pull more developers over to using CF.