Login problems after publishing (sql express server)

Thanks for taking your time to read this.(sorry if someone posted this earlier but no solutions helped)

After i published my website, i am unable to login anymore. It has this error of "Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed."

Note ** im using vb

This may cuased by the IIS account (5.0 is ASPNET and 6.0 is NT AUTHORITY\NETWORK SERVICE) used to connect to SQL is not allowed to generate the user instance. I'm sorry to say that I don't know how to give the permission to the account, maybe you can try to add the IIS account to local machine Administrators group. But I always use a workaround: remove the User Instance attribute from your connection string as I do not need it. To know more about connection string, you can visit this link:

http://msdn2.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring(d=ide).aspx

Login problem publishing to my machine from VS2005

So I'm trying my first Report project from Visual Studio 2005 and I
get a good connection string and run the project. When I run it it
tries to deploy to http://localhost/reportserver, and asks for a login
and password. But nothing works. I don't even think I have a password
set up for reporting services on this machine.
Once it fails and I run it again, it runs fine in local mode on my
machine. Does anyone know what is going on here?So this never happens to anyone else? Very weird. Maybe it's time to
just format the damn thing and install everything again.