SAP Netweaver Studio do not work anymore...

After 2 hours of comfortable utilisation, including closing and re-opening, my netWeaver Studio close suddenly and from that point i could not start it anymore.

I have always the same issue: "Problem during startut, check the log".

And log told me

MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.ui.workbench".

Do anyone encoutner the same issue? Does anyone know how could i "reset" my metadata to start-up again?

thanks.

Guillaume