Extending the LPEX editor

I tried to create an extension for the LPEX editor, following the 
guidelines from Eric Simpson (the "Hello World" example). The example was 
for 4.0; I am using 5.1 so some of the details have changed (e.g. no 
.classpath file, but an option "Update classpath ..."). Of course I did 
not use "yourcompany" and "HelloWorld", but my own initials and a silly 
name, and of course the thing did not work. So I had a retry with the 
exact names as Eric wrote them, but it still does not work. Everything 
compiles fine; when I run it with "Run-time workbench" I get a second 
instance of Eclipse. But when I start LPEX and enter HelloWorld on its 
command line it tells me '"HelloWorld" is not a valid editor command.' I 
tried setting a breakpoint on the first line of the startup() method ( 
super.startup() ) and running through 'Debug Run-time Workbench' but that 
does not change anything, which suggests that the startup() method is not 
executed. How can I find out what is going on?

Joep Beckeringh