Seen with 
Product Version: NetBeans IDE Dev (Build 200710301200)
Java: 1.5.0_11; Java HotSpot(TM) Client VM 1.5.0_11-b03
System: SunOS version 5.10 running on x86; ISO646-US; en (nb)
Userdir: /Users/lautz/.netbeans/dev

Not sure whether this is related to issue 120681, but I only see the exception if I try to add in new consume and
provide endpoints after encountering the problem described in issue 120681. I do not have exact reproduceable steps, but
will include the messages.log showing an error and the uigestures file.

1. Create a new SynchronousSample sample app.
2. Open SynchronousSampleApplication in the CASA editor.
3. DnD a new External from the palette to the External Mmodule area.
4. Rename the external module by changing the name property in the properties dialog and clicking Close.
5. Using the context menu for the external module, add a consume and provide endpoint.
6. Rename the endpoints. (Doesn't seem to matter.)
7. Save. (This doesn't seem to matter.)
8. Click the Build Project button.

=> The endpoints disappear.

9. Add the provide and consume endpoints again. Click build project. Add a few more consume and provide endpoints.

=> IllegalArgumentException dialog shown.