Creating an instance of an object implemented by COM LocalServer freezes

Creating an instance of an object implemented by COM LocalServer freezes

I have created a COM object server exe which implements a COM Object, and
calls to CoRegisterClassObject, and then sleeps for a long time (to
prevent the process from exiting)
After running it, I have another COM client exe which calls to
CoCreateInstance with the CLSID of the object registered previously on
CoRegisterClassObject,
CoCreateInstance freezes the thread, but if I close the COM Server process
- then CoCreateInstance returns immediately with "Class not registered.".
Do any of you know what's going on?
Thank you.