Import OBJ is working now fine. Thank you for your help.
Unfortunately export is not working like before.
--------------------------------------------------------
log after export:
--------------------------------------------------------
Traceback (most recent call last):
File "Libs/python3.1/morphospath.py", line 140, in split
i = p.rindex(sep)
ValueError: substring not found
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "MorphOS:Applications/Blender257a/2.57/scripts/addons/io_scene_obj/__init__.py", line 121, in execute
return export_obj.save(self, context, **self.as_keywords(ignore=("check_existing", "filter_glob")))
File "MorphOS:Applications/Blender257a/2.57/scripts/addons/io_scene_obj/export_obj.py", line 797, in save
EXPORT_PATH_MODE=path_mode,
File "MorphOS:Applications/Blender257a/2.57/scripts/addons/io_scene_obj/export_obj.py", line 741, in _write
EXPORT_PATH_MODE,
File "MorphOS:Applications/Blender257a/2.57/scripts/addons/io_scene_obj/export_obj.py", line 290, in write_file
file.write('# Blender v%s OBJ File: %r\n' % (bpy.app.version_string, os.path.basename(bpy.data.filepath)))
File "Libs/python3.1/morphospath.py", line 186, in basename
return split(p)[1]
File "Libs/python3.1/morphospath.py", line 145, in split
i = p.rfind(altsep)
UnboundLocalError: local variable 'altsep' referenced before assignment
location:<unknown location>:-1
location:<unknown location>:-1
---------------------------------------------------
text from second output window:
---------------------------------------------------
OBJ Export path: 'MorphOS:Stuff/3D/cube.obj'
----------------------------------------------------
Exported file has 0 bytes.