Answer
Yes. While the geometric network creation process can identify and sometimes correct issues that can cause network inconsistencies, there is one scenario that can lead to inconsistencies; polyline geometries with coincident vertices at either of its endpoints. This scenario has been addressed in ArcGIS 10.0, but can still occur in earlier releases. The geometric network creation process in 9.3.1 and earlier releases is not able to identify and correct this issue, which can lead to network inconsistencies following network creation.