When a point, polygon, text, or other Redline feature is published to the server from the Silverlight viewer, the publish does not succeed. The new feature is not added to its respective table.
It is possible that the server is rejecting the edit. Using Fiddler to sniff the HTTP call generated by the Silverlight page, and then using that sniffed URL in a browser should yield more information specific to the situation.
One likely cause is that the redline dataset is ArcFM'ified, but the redlines service does not have the ArcFMMapServer capability added to it, and thus cannot perform edits against ArcFM features.
The solution in this instance is to add the ArcFMMapServer capability to the redlines FeatureService. The steps to do this can be found here.
Alternatively the issue could be related to #NIM085553 - a database locking issue when posting with feature services. This is fixed in ArcGIS Server 10.2, and QFE-101SP1-S-250483 fixes it in ArcGIS Server 10.1 SP1.