Using the Extend\Trim commands or the Extend\Trim Features task in ArcMap Editor can cause network inconsistencies when used on complex edge features. This results in the endpoint of the edge being extended or trimmed without its connected junction, leaving the connected junction in its original location.
To prevent this from happening again, download and install ArcGIS 9.2 Service Pack 4.
To correct any existing instances of this issue, use the Rebuild Connectivity tool over the feature that was extended or trimmed. The junction feature that remains at the original endpoint of the edge feature needs to be deleted or moved to the new endpoint.