If user.config file exists in the root it will use the connection string setting from there instead of web.config. If user.config does not exist you should create it by renaming user.config.sample (which does exist) as user.config, then put your connection string there instead of web.config. This way you won't lose custom settings such as connection string when you later upgrade to a new version of mojoPortal.
If you still get this error after putting the connection string in user.config then you should ask your host for help because the error indicates that the web server cannot connect to the database server.
You should not post your database connection credentials in a public forum as it could be used by others to connect to your database, so I hope what you posted is not exactly correct. If you did I would suggest see about deleting that database user and creating a new one.
I would suggest format your connection string like this:
<add key="MSSQLConnectionString" value="yourserver;UID=youruser;PWD=yourpassword;database=yourdbname" />
Note that you posted single quotes around the password, you should not have those single quotes.
Hope that helps,
Joe