trouble while suppressing all virtual sites

Hello,

I have some trouble after suppressing the last virtual site on a Jahia
server 4.0.4 (in a preparation to a migration toward the 4.0.5
version): migration was ok, but I have now the message: "the virtual
site has not been found": then I want to force the access to
administration pages, in order to be able to create a new virtual
site, but after entering user/pwd, the login page display again and
again , and I have no more access to Jahia administration.
Do you have a hint to create this virtual site manually, or am I
oblige to reinstall the whole Jahia version 4.0.5 ?

Thanks by advance !

Dominique Pellat