OCI driver fails to resolve service name

[ayanafridi]

I am using Oracle 9i OCI drivers to connect a java app to an oracle DB. The app is running on Weblogic8.1

The issue is this: When I deploy the application, the connections open just fine to Oracle 9i, using the oci drivers. But eventually they fail, and I get these TNS:could not resolve service name errors.
Initially, in the WebLogic start scripts, I am setting three variables for oci to work: ORACLE_HOME, LD_LIBRARY_PATH, and PATH.
I know these are all set correctly because I can connect through the app server to the database for the initial few days. Then for some reason out of the blue, I get the errors from WebLogic attached below:

#### <> <> #### <> #### <> java.sql.SQLException: ORA-12154: TNS:could not resolve service name

Has anyone else had this issue, or have any idea how to pursue this issue?
Help appreciated.