open the WTK (Wireless ToolKit)
open ur project
just go to setting menu>
Midlet
there u will find the following fields that are editable:
midlet name field, midlet icon field, and midlet class field(which is the classpath and there's your problem)
you have to specify class path again in that loaction by clicking Edit at the bottom of the window.
suppose your main midlet is in package
Greeting and ur midlet class name is
TinyMIDlet
then u have to specify same in midlet class field as
Greeting.TinyMIDlet, and don't forget the dot(.) here
NOTE : if there is no package declared in the source file, just ignore the name and write just your midlet class name..
i hope this will help u and update me if there is any difficulty.

Peace.
sakr232000 at yahoo dot co dot in