Dont know if this is still relevant, perhaps another sailor will find this useful.
The message appears when one has a class file compiled the debug flags turned off.
In eclipse, you can turn it on by the afore mentioned options,
Window --> Preferences --> Java --> Compiler --> Classfile Generation: "add line number attributes to generated class file"
But if you have a jar file, then you would get the compiled output. There is no easy way to fix this problem.
If you have access to the source and use ant to get the jar file, you may modify the ant task as follows.
<javac destdir="${build.destDir}" srcdir="${build.srcDir}" source="1.6" fork="true" target="${javac.target}" debug="on" debuglevel="lines,vars,source" deprecation="on" memoryInitialSize="512m" memoryMaximumSize="1024m" optimize="true" >
Happy debugging..