[news.eclipse.platform.rcp] Problem after export Eclipse product

[badr <badreddine49@xxxxxxxx>]

I developed an RCP application, and i create and launch its product  through Eclipse but when I want to export this produc. i obtain the following message:

!MESSAGE An error occurred while automatically activating bundle org.medcolourtech (14).
!STACK 0
org.osgi.framework.BundleException: The activator org.medcolourtech.MedColourTechPlugin for bundle 

org.medcolourtech is invalid	
	at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadBundleActivator(AbstractBundle.java:141)
.......
Caused by: java.lang.ClassNotFoundException: org.medcolourtech.MedColourTechPlugin 
	at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:407)
...........
Root exception:
java.lang.ClassNotFoundException: org.medcolourtech.MedColourTechPlugin 
	at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:407)
.........
!ENTRY org.eclipse.osgi 4 0 2008-10-08 00:28:21.406
!MESSAGE Application error
!STACK 1
org.eclipse.core.runtime.CoreException: Plug-in org.medcolourtech was unable to load class org.medcolourtech.MedColourTechApplication.
.............
	at org.eclipse.core.launcher.Main.main(Main.java:952)
	org.eclipse.core.runtime.CoreException[1]: java.lang.ClassNotFoundException: org.medcolourtech.MedColourTechApplication
	at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:407).

..............
Any help would be appreciated! 

Thanks, 
Badr