Hello Sean:Thanks for the suggestion, but unfortunately it did not solve the problem. Here is the code that sets up the edit sketch. It's the same for both Tool A and Tool B.
m_editSketch = m_editor as IEditSketch2;
m_editSketch.GeometryType = esriGeometryType.esriGeometryPolygon;
m_editEvents = (IEditEvents_Event)m_editor;
m_editEvents.OnSketchFinished += new IEditEvents_OnSketchFinishedEventHandler(m_editEvents_OnSketchFinished);
m_editor.CurrentTask = null;
A little more information that might be helpful: if I put a breakpoint on the OnSketchFinished event for tool B, on entry to the event handler the editor and the edit sketch are null items, so the edit sketch geometry is null as well - as if the editor and edit sketch have been consumed by some event handler left over from Tool A.