OK,
i have figured it out.
it was the red Line, which caused the error:
QString Dir = G_cWorkSpace.fiModelsDirectory.absoluteFilePath();
fiCalculatingDirectory is from Type: QFileInfo, in my class WORKSPACE...
void Tab1::on_pushButtonSelectFiles_clicked()
{
QString Dir
= G_cWorkSpace.
fiModelsDirectory.
absoluteFilePath();
//caused the error ...
}
void Tab1::on_pushButtonSelectFiles_clicked()
{
QString Dir = G_cWorkSpace.fiModelsDirectory.absoluteFilePath(); //caused the error
QFileDialog dialog( this,Dir,"(*.inp)");
...
}
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changing it to:
void Tab1::on_pushButtonSelectFiles_clicked()
{
Dir = G_cWorkSpace.fiModelsDirectory.absoluteFilePath(); // problem solved
...
}
void Tab1::on_pushButtonSelectFiles_clicked()
{
QString Dir;
Dir = G_cWorkSpace.fiModelsDirectory.absoluteFilePath(); // problem solved
QFileDialog dialog( this,Dir,"(*.inp)");
...
}
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solved the problem 
thanx & greetz to All,
Astronomy
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