main class could not be found?

[System_Error]

I've created a jar file like this:

jar cfmv Manifest.mf RoboPlot.jar RoboPlot.class ImagePlotter.class

The manifest.mf file looks like this:


Main-Class:RoboPlot

For some reason, when I use this command to run it,
java -jar RoboPlot.jar

it tells me that the main class could not be found

I also tried this:

Manifest-Version: 1.0
Created-By: 1.5.0 (Sun Microsystems Inc.)
Main-Class:RoboPlot

and it didn't work either.