Struggling with populating fields into related custom objects

Well we are able to add from a table row, and populate the necessary fields. The problem that I have come to find out, is that when in edit mode the conditions act as defined values from the existing object, but when in read mode, they are conditions and act to control what you can see. By using the conditions, if someone blanks out a value used in the conditions and saves the record, well although the record does get created, they cant see it. For instance, we have a service that may or may not have a username and email address. When a client calls to create a case, sometimes it is the user that created the service and sometimes not. If we populate a field in the table with these values and they are blank when saved, the case disappears from the service, although you can still see it when using standard SF views. A little confusing but our app is quite complex and uses mostly custom objects. Guess we have to try and send using a url with the parameters to set the fields in the url.