[2005] error while trying to run project: Unable to start debugging

Hi;
I have installed VB.Net exp. ed. to my friends pc. The problem is that I was teaching him how to start programming. In the first time we have selected a windows application then he deleted the main form. He put a dialog and he got an error. Bla bla... I tried to fix it but as we tried to run the project we got this error:
error while trying to run project: Unable to start debugging
bağlama işleci geçersiz (eng: connection operator is invalid)

So I have thought that we couldnt fix the problem with main form and I have started another project. But the problem was the same. How can we solve this issue?

Thanks very much

So the problem persists even with a blank new project?

yes it persissts even with a blank project. Is it a bug or an error specific for that pc?

isnt there any solution?