Apparently that area has been unchanged for a while as the sample files in v13.3 XOG are from verions 6 and 7.
When you tried to write timeperiods (you can only write timesheets in v14.2) you used this structure
<TimeSheetEntry assignmentFinish="2002-07-12T17:00:00" taskID="~rmw" assignmentStart="2002-05-13T08:00:00" chargeCodeID="DEV" assignmentPendingEstimate="0" assignmentID="5000015" projectID="TIMESHTGAMES" assignmentEstimate="360"><DailyActuals><Actual actualDate="2002-06-02" amount="0"/><Actual actualDate="2002-06-03" amount="2"/>
and your userID had also enter time for the user in question?
When trying to write the assignment etc did you use the following structure
</Resource></Resources><Tasks><Task finish="2004-12-16T17:00:00" internalTaskID="5018150" key="false" lastUpdatedBy="sbutler" lastUpdatedDate="2004-09-16T11:03:00" milestone="false" name="Effort" orderID="1" outlineLevel="1" percComp="0" start="2004-09-16T08:00:00" status="0" summary="false" taskID="~rmw"><Assignments><TaskLabor actualWork="0" baselineWork="0" estPattern="3" finish="2004-12-16T17:00:00" lastUpdatedBy="sbutler" lastUpdatedDate="2004-09-16T11:05:34" remainingWork="528" resourceID="PRJ_COVRG_ASSIGN_RES1" roleID="PRJ_COVRG_ASSIGN_ROLE" start="2004-09-16T08:00:00" unpostedActuals="0"><CustomInformation/>
and again did the userID have the rights edit project plan among others?