[news.eclipse.tools] No Breakpoint Marker Bar in JDK core source files

[cgcjm@xxxxxxxxxxxxxxx (rhubarb)]

Sorry, but I did try to RTFM.

I am trying to set breakpoints inside jdk core source and swing files.
(E.g. inside java.awt.Component or javax.swing.JComponent)

I am running jdt on eclipse M4 with jdk1.4.1_01.

I have compiled all of the jdk source files in debug form and zipped these
into a jar called debugClasses.jar.

I went to Run->Debug->Classpath->Bootstrap classes and put my
debugClasses.jar at the top.

But still, when I step into a java or swing class I can't add a breakpoint
because I cant add a breakpoint (no ctrl-Shift-b and no breakpoint marker
bar).

I tried adding my debugClasses jar both as an internal and external jar.
And I made sure that the sources were in the source path.

What am I doing wrong - I am sure I've had this working before.

thanks
rhubarb