increased the Delay much more (now 1.5s).

Lower Delay will rise errors when rendering big images. 
My system Win7 64 (slow HD) reports following error on lower Delay: 
---
Reached EOF while decoding PNG
Cannot open input file
Cannot create backend data
Unknown fileformat
---

Maybe Delay should be bound to the imagesize. Or is there a better solution to wait for povray to finish the writing?

render_povray/render.py

@@ -1427,7 +1427,7 @@ def write_pov_ini(filename_ini, filename_pov, filename_image):
 class PovrayRender(bpy.types.RenderEngine):
     bl_idname = 'POVRAY_RENDER'
     bl_label = 'POV-Ray 3.7'
-    DELAY = 0.2
+    DELAY = 1.5
     
     def _export(self, scene):
         import tempfile