Cannot connect source when using external folder (eclipse)

I am working on an Eclipse project (Eclipse 3.6.2 + Android ADT + BlackBerry plug-in), where I need to split the code between Android, BlackBerry and JavaSE projects.

I moved the platform-independent code to a separate folder and created the following structure

CoreCode - java project
  - /src - platform independent code

CorePlusDroid - Android library project with core code plus Android-specific classes 
  - /src - Android-specific code   
  - /core_src - linked source from CoreCode/src (via Source tab in Java Build Path)

DroidApp - Android application that uses CorePlusDroid library
  - /src
  - /gen
  - /assets
  etc

DroidApp builds and works fine, but when I try to switch to classes from CoreCode or enter one of them with a debugger, I get the "Source Not Found" page. I tried to click the "Change the attached source ..." button and set the path to / CoreCode / src or specify this folder as an external folder, but nothing helps. The editor still cannot find the source code for the classes in CoreCode / src.

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