Fatal in <TClass::TClass>: ROOT system not initialized

Dear rooters,
On Suse linux 8.2 and ROOT 4.00/08, after the necessary includes and initializing the ROOT system first, I get this error. In fact the application works fine and only "gApplication->Terminate(0);" causes the problem.
I do

#include <TROOT.h>
#include <TSystem.h>
#include <TApplication.h>
#include <TGClient.h>
#include <TGFrame.h>

int main(int argc, char **argv){

	TApplication theApp("App", &argc, argv);
	//GUI pops up
	App.Run();
	//do some plots/calculations
	//GUI pops up
	//pressing a button calls
CloseWindow(){gApplication->Terminate(0);}
	return 0;

After some printout before and after the Terminate() I see only the first one.
Do I miss anything?

Best regards

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