I always seem to have problems with jars myself. I presume you have set a "main" class when you created the jar from Eclipse. I presume you have had to add Openswing to the classpath with the "use external jars" command on Eclipse.
Please go through the Java Tutorials about "deployment", and find the bit about adding to the classpath; then you can put Openswing into the same folder and the new classpath will allow it to find it.
There is a cheat's way of putting a jar into the classpath, which is to move an openswing folder into the package structure.Try executing the main method from such a folder structure. It is in theory possible to add the classes in the openswing folder to the jar with the updating commands (see the tutorial link I posted above), but I have never tried myself. [ May 26, 2008: Message edited by: Campbell Ritchie ]