How are you calling the CFC from Flex? Through RemoteObject calls or through the generated code from the Data Menu -> Connect to ColdFusion?
At the outset looks like the CFC file is not getting compiled to be accessed through RemoteObject.
I started with an empty Data/Services view and clicked the link "Connect to Data/Service" I selected ColdFusion, browsed to the CFC in the ColdFusion Component section and used the default service name and package that it created. I clicked next, entered my login information and clicked Finish on the screen that showed the operations in the service.
I tried this with the original beta SDK, 126.96.36.19934 and 188.8.131.5204
The original issue described used the original beta SDK
184.108.40.20604 & 220.127.116.1134 errored with VerifyError #1014: Class IVisualELement could not be found, ReferenceError: #1065: Variable CrossFade_CrossFadeShaderClass is not defined, ReferenceError: #1065: Variable Wipe_WipeShaderClass is not defined, and ReferenceError: Error #1065: Variable _2e124f77eedc07babaa6f5d7b8f173c364f54221c2a0cd01c6886c90f93a6fbf_flash_display_Sprite is not defined. Additionally, every time I edited anything, the Flash Builder app returned an error that said "An internal build error has occurred. Right-click for more information" which seems to require a restart of Flash Builder to resolve.
I didn't have time to continue trying to figure out what about my code, setup or plugin was causing all those problems with the SDKs, so I gave up with testing in them.
I attached the MXML file I used and the cfc I used in my tests.
TestMapping.zip 907 bytes
This is not an issue with Flex.
There seems to be a compilation issue once the CFC is changed.
Work-around: Use "Refresh" service in DCD - this would actually re-compile your CFC.
a) Create a Flex-CF project in FB.
b) In the Data/Services panel click on "Data/Services"
c) Select "ColdFusion" and click NEXT.
d) Click "Browse" to select the "pxTestMapping.cfc" ,click NEXT and FINISH.
e) Context click on the function(helloworld()) and select 'Test Operation', hit 'Test', now you should see "Hello World Updated1"
f) Now change your return in CFC to "Hello World Updated"
g) In FB, context click on "PxTestMapping" service and select 'Refresh'
h) Now perform "test Operation", you should see the updated return value ie "Hello World Updated".
Hope this helps!