Gallery 2.3.1 & Oracle 10.2

I am attempting to install Gallery 2.3.1 and use an existing installation of Oracle 10.2. However, when I try to complete the setup page, I always get the following error:

Warning: ocinlogon() [function.ocinlogon]: OCIEnvNlsCreate() failed. There is something wrong with your system - please check that ORACLE_HOME is set and points to the right directory in /home/www/doc/gallery2/lib/adodb/drivers/adodb-oci8.inc.php on line 224
oracle: Connection error to server 'oracle' with user 'gallery'

I have verified that the PHP (version 5.2.0) oci8 module is working properly by running the oci8 tests with the same username & password I am supplying in the Gallery installer. For the PHP tests, I set the $dbase variable to the same as my TWO_TASK environment variable. Perhaps that is the problem? Does Gallery not use TNS? If not, what exactly should I specify in the installer's DB Hostname & DB Name fields?

I read the Gallery2:Oracle page in the wiki, and I think I'm in line with those recommendations for the most part.

Is there additional failure information saved in a log file somewhere, and if so, where?

Any suggestions would be very much appreciated.

Thanks,
Bill