Did you follow those quick start steps exactly? Usually the only way to end up with missing lines is that one of the point features in the geometric network is missing from the configuration. Schematics needs to have configuration information for every class that is in the geometric network in order to keep proper connectivity. A link can't exist without both end nodes. So if one of those end node classes hasn't been configured, it won't work. If you haven't followed those steps exactly, give it a quick try with a file gdb or personal gdb and see if that resolves it, only takes a minute or 2 to test it. If that still doesn't fix it, let me know and we can try to setup a web meeting so I can see what is happening. Also include the service pack you are running in the next response please.
