请教高手我这段程序错在哪,有时行有时就不行??

Sub drawneiwaique()
'画椭圆弧
Dim startpt(0 To 2) As Double
Dim pi As Double
pi = 4 * Atn(1)
Dim ellobj As AcadEllipse
Dim ellmajoraxis(0 To 2) As Double
Dim ellcenter(0 To 2) As Double
startpt(0) = 0: startpt(1) = 0: startpt(2) = 0
ellcenter(0) = startpt(0) + 25: ellcenter(1) = startpt(1) + 15: ellcenter(2) = 0
ellmajoraxis(0) = startpt(0) + 25: ellmajoraxis(1) = startpt(1): ellmajoraxis(2) = 0
Set ellobj = ThisDrawing.ModelSpace.AddEllipse(ellcenter, ellmajoraxis, 0.6)
ellobj.StartAngle = 0.5 * pi: ellobj.EndAngle = 1.5 * pi
'画直线
Dim plinept(0 To 11) As Double
Dim plineobj As AcadPolyline
Dim ellendpt As Variant
Dim ellstartpt As Variant
ellendpt = ellobj.EndPoint
ellstartpt = ellobj.StartPoint
plinept(0) = ellendpt(0): plinept(1) = ellendpt(1): plinept(2) = ellendpt(2)
plinept(3) = ellendpt(0) + 25: plinept(4) = ellendpt(1): plinept(5) = 0
plinept(6) = ellstartpt(0) + 25: plinept(7) = ellstartpt(1): plinept(8) = 0
plinept(9) = ellstartpt(0): plinept(10) = ellstartpt(1): plinept(11) = ellstartpt(2)
Set plineobj = ThisDrawing.ModelSpace.AddPolyline(plinept)
'建立面域
Dim shapeobj(0 To 1) As AcadEntity Dim regionobj As Variant
Set shapeobj(0) = ellobj
Set shapeobj(1) = plineobj
regionobj = ThisDrawing.ModelSpace.AddRegion(shapeobj)
ellobj.Delete
plineobj.Delete
End Sub