Import Arcpy error

Hi everyone,
I've searched the forums and the internet for an answer to this, but unfortunately I've had no luck.
I'm running Arc 10.1 sp1

Regardless of whether I use Idle, pythonwin, pyscripter or the built in python editor window in Arc, I get the following error when I try to import arcpy

>>> import arcpy
Runtime error
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\__init__.py", line 24, in <module>
from arcpy.toolbox import *
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\toolbox.py", line 342, in <module>
from management import Graph, GraphTemplate
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\management.py", line 22, in <module>
import _management
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\_management.py", line 14, in <module>
import _graph
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\_graph.py", line 27, in <module>
import numpy
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\__init__.py", line 137, in <module>
import add_newdocs
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\add_newdocs.py", line 9, in <module>
from numpy.lib import add_newdoc
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\lib\__init__.py", line 4, in <module>
from type_check import *
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\lib\type_check.py", line 8, in <module>
import numpy.core.numeric as _nx
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\core\__init__.py", line 8, in <module>
import numerictypes as nt
File "C:\Python27\ArcGIS10.1\lib\site-packages\numpy\core\numerictypes.py", line 92, in <module>
from numpy.core.multiarray import typeinfo, ndarray, array, \
ImportError: cannot import name datetime_data

The python installation is not a standalone one, it is the one installed when installing Arc,
so in the python27 folder within the C drive, there is only 1 folder, this is ArcGIS10.1.

Therefore I am unable to carry out the fix provided by Kimo in post #2 here
http://forums.arcgis.com/threads/215...ll=1#post10859


I've also looked at the contents of the Desktop10.1.pth file and the file paths seem correct ( as specified in the Tip at the bottom of this page http://resources.arcgis.com/en/help/...00000008000000 )

I have 3 lines in this file, as below:
C:\Program Files (x86)\ArcGIS\Desktop10.1\bin
C:\Program Files (x86)\ArcGIS\Desktop10.1\arcpy
C:\Program Files (x86)\ArcGIS\Desktop10.1\ArcToolbox\Scripts

Any ideas what I can do next to try and get arcpy to be recognised?

Many thanks

Dan