Erro ao executar arquivo ".jar"

Opa amigos, fiz um projeto pra meu TCC que se trata de uma tabela periodica

eh um software interdisciplinar e talz, fiz td no netbeans.

Dentro do netbeans funciona redondo, soh q qdo tento executar apartir do arquivo ".jar"

que mando construir apresenta esse erro aew:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

 at javax.swing.ImageIcon.<init>(Unknown Source)

 at br.home.project.tableGUI.PeriodicTable.initComponents(PeriodicTable.j

ava:279)

 at br.home.project.tableGUI.PeriodicTable.<init>(PeriodicTable.java:44)

 at br.home.project.tableGUI.PeriodicTable$125.run(PeriodicTable.java:209

1)

at java.awt.event.InvocationEvent.dispatch(Unknown Source)

at java.awt.EventQueue.dispatchEvent(Unknown Source)

at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.run(Unknown Source)

alguém pode me explicar o porquê?!

Agradeço.