Is arcpy expected to have no problems when running inside virtualenv? Definitely issues with numpy, but graphs as well...
>>> import arcpy
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\__init__.py", line 25, i
n <module>
from arcpy.toolbox import *
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\toolbox.py", line 342, i
n <module>
from management import Graph, GraphTemplate
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\management.py", line 22,
in <module>
import _management
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\_management.py", line 14
, in <module>
import _graph
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\_graph.py", line 27, in
<module>
import numpy
ImportError: No module named numpy
>>>