That *IS* strange!
First, verify that you are connected to the internet.
Second, verify that you have web apps set up in Hana. No web-apps means no main window.
Third, verify that you have at least one web-app set to active. No active web-apps means no main window.
Fourth, using a web browser, verify that the addresses entered for one or more of your web-apps works.
Fifth, using your web browser, visit AllOutSoftware.com and visit the Hana Support page. If you find no help there, then please, PLEASE let us know. We want to make sure you are happy with Hana!