Your blank site as specified by STS#1 should be a blank page (i.e. SharePoint page with no content). If you are getting a "page not found" error, then something went wrong when you created the site collection, even though it told you that it was successful. This would also lead to the subsequent errors when creating the subsite.
I notice that you did not specify a secondarylogin. This is a required field unless you are using Active Directory account creation mode. If you are using this, then ownerlogin and secondarylogin should not be specified. (
http://technet.microsoft.com/en-us/library/cc262594(office.12).aspx)
If possible, I suggest that you delete the site collection and start over using Central Administration to create a new site collection. If you continue to get errors, there may be something wrong with the STS#1 site definition. You might try creating a different one just to make sure that something else isn't wrong.
Hope this helps.