Blender ImportError cannot import name

I am really almost giving up on trying to create an import-export module
to Blender 2.68 and it seems that it is an insurmountable python problem (Blender uses python 3.3). I have googled plenty of questions on this topic but none of them answers my problem. Part of my script:

if “bpy” in locals():
import imp
imp.reload(xplane_ui)
print (“xplane_ui reloaded.”)
imp.reload(explane_import)
print (“All modules reloaded.”)
else:
import bpy
from io_xplane import xplane_ui
print (“xplane_ui imported.”)
from io_explane import explane_import #this is line 47
print (“All modules imported”)

I added extra print lines to see what is happening. Here is the trace result:

Read new prefs: C:\Users\BT<i>AppData\Roaming\Blender Foundation\Blender\2.68<i>config[/userpref.blend
found bundled python: C:\blender-2.68a-windows32\2.68\python
xplane_ui imported
All modules imported
xplane_ui imported.
Traceback (most recent call last):
File "C:\blender-2.68a-windows32\2.68\scripts\modules<i>addon_utils.py, line 294, in enable
mod = import(module_name)
File "C:\blender-2.68a-windows32\2.68\scripts<i>addons</i>io_explane_init.py, line 47, in <module>
from io_explane import explane_import
ImportError: cannot import name explane_import

This is so queer. I presume python progresses from top to bottom but how would it progress through lines 46, 47 and 48 and then change decision on line 47 and announce it could not do it after having obviously done it?

I tried inserting another know good file from another addon and it loaded OK.
Then tried renaming this file to explane_import and it still loaded OK.
This suggests that the real problem is that blender rather than python is rejecting my file due to something in the contents of my file but blender is incapable of stating the nature of the error.
In view of this the question should probably be deleted if it is not considered useful to other users.