I\'ve downloaded the source for all the Maven JARs in my buildpath using Maven->Download Sources and mvn eclipse:eclipse -DdownloadSources=true
, which worked! W
In my case the problem was related with the source code attached with the "Debug Configuration", maybe some remnants form a migration to Maven.
I solved it by going to the "Debug Configurations..." page and selecting the configuration in case, then at the "Sources" tab I restored the defaults, which added all the project's Maven dependencies.
Although this bug had the most votes of all bugs @Sonatype, it hasn't been fixed.
However I have filled an enhancement request on Eclipse Bugzilla and if you agree this issue "Source not found" should be fixed, please vote for it here.
You can found three workarounds here.