That class is missing in the classpath. Check your %CLASSPATH% environment variable, check the current working path, check the -cp or -classpath parameter (which are in fact overriding the %CLASSPATH% environment variable), check the JAR´s manifest. For a more detailed answer, you need to give more detailed information.
After all I would consider this as a "Java in general (Beginner)" question.
Lucas Franceschi wrote: //there's no reason to be aggresive with a fellow rancher, Bauke...
I didn´t shoot him off or so? Were you referring to the last sentence? I don´t know what you think, but how the classpath works is covered by every decent Basic Java book/tutorial. So I don´t see how you see it as agressive.
means that this JAR file needs files named appframework-1.0.3.jar and swing-worker-1.1.jar in a lib/ directory sitting next to it to run. These things must be installed on the other machine where it works.