OCIEnvCreate failed with return code -1 + Windows Form + Windows 7 64bits

OCIEnvCreate failed with return code -1 + Windows Form + Windows 7 64bits

I have this situation:
An old windows forms system (from a client), done with VS 2008 and
Framework 3.5, accessing Oracle Database ERP (12g)
Cause we don't have VS 2008, the solution was migrating to VS 2010, and it
is now installed on a notebook running Win 7 64Bits. It continues to use
framework 3.5, but now it is compatible with VS 2010.
The original project, was using Oracle 32 bits OTP driver. My notebook is
Win 7 64 bits, but it has the 32 bits version installed (from
ODTwithODAC1120320_32bit.zip package). This package was installed cause
other system uses it. I Think this is the correct drive.
The original application was done by an employee that is out of client's
company, and they need to inscrease functionalities in this application.
The migration process was 100% and the project is compiling in VS 2010.
The only problem is that when we run the system, it tries to execute the
first query and the error below appears:
OCIEnvCreate failed with return code -1 but error message text was not
available
I have already searched google, and get so many suggestions. I have
already done:
have installed 64 bits version of Oracle Odac (from file
ODAC1120320_x64.zip).
have changed permission access to Oracle Home folder (in my notebook is
ORACLE_HOME=C:\app\marcelo.oliveira\product\11.2.0, to garantee correct
permissions
inserted the user 'network services' with the same permissions as
'authenticated users'
inserted all oracle paths (32 and 64 bits) on environment variable PATH
Nothing take effects.
Some questions:
My client needs to be 12g as the database ? If this is the problem, may I
have 11.2 and 12 living together in my Win 7 ?
Is it necessary to have both 32 and 64 bit versions installed ? I have
installed, but I am not sure this is necessary
The migration to VS 2010 could be the reason for this problem ?
Some notes:
I have SQL Developer program installed and I can access the oracle ERP
from there.
I am using TNS file to connect. Cause I can access from SQL Developer with
this TNS file, I understand it is correct.
I have lost 3 days up to now, and I really dont know what more is
necessary to resolve it... I really appreciate any help.
Thanks, Marcelo de Oliveira.