The 3.0.2 installation writes the wrong user name when you install using an impersontated user. Instead of writing the username I specified in the install, it seems to have used sgvaultuser in the Web.config file (see example line below).
<identity impersonate="true" userName="sgvaultuser" password="safepswd"/>
fixing that attribute value, allowed me to log in.
3.0.2 Server install impersonate bug
Moderator: SourceGear