cx_Oracle 5.1.1 under apache+mod_wsgi
Need a solution as well.  
I have the same setup on WinXP (Apache 2.2.21/ mod_wsgi 3.3/ python 2.7.2/ cx_Oracle 5.x.x).  I found that cx_Oracle 5.1 also fails with the same error.  Only 5.0.4 works.  
Here is the list of changes that were made from 5.0.4 to 5.1:

Remove support for UNICODE mode and permit Unicode to be passed through in
everywhere a string may be passed in. This means that strings will be
passed through to Oracle using the value of the NLS_LANG environment
variable in Python 3.x as well. Doing this eliminated a bunch of problems
that were discovered by using UNICODE mode and also removed an unnecessary
restriction in Python 2.x that Unicode could not be used in connect strings
or SQL statements, for example.
Added support for creating an empty object variable via a named type, the
first step to adding full object support.
Added support for Python 3.2.
Account for lib64 used on x86_64 systems. Thanks to Alex Wood for supplying
the patch.
Clear up potential problems when calling cursor.close() ahead of the
cursor being freed by going out of scope.
Avoid compilation difficulties on AIX5 as OCIPing does not appear to be
available on that platform under Oracle 10g Release 2. Thanks to
Pierre-Yves Fontaniere for the patch.
Free temporary LOBs prior to each fetch in order to avoid leaking them.
Thanks to Uwe Hoffmann for the initial patch.
if I use cx_Oracle 5.0.4, I can connect from python console, and works under apache+django+mod_wsgi
but when I update cx_Oracle 5.1.1, I can connect from python console, BUT same code doesn't work under apache+django+mod_wsgi
File "C:\Python27\lib\site-packages\django\db\backends\oracle\base.py", line 24, in 
     raise ImproperlyConfigured("Error loading cx_Oracle module: %s" % e)
 TemplateSyntaxError: Caught ImproperlyConfigured while rendering: Error loading cx_Oracle module: DLL load failed: The specified module could not be found. 
PS: python 2.7 
PSS: I have instaled MSVC 2008 Redistributable x86