Error connecting to oracle database

We have developed an ActiveX Dll in VB that connecting to oracle database. It works in VB environment, but does not work when it was called by PowerBuilder code at the same machine. The error we got is "-2147221504: Oracle error occured, but error message could not be retrieved from oracle". We suspect it has something to do with TNSNAMES.ORA, initially we thought it had something to do with MDAC, after we clean up everything and just have MDAC version 2.5, we still got the same error. Any suggestions and help will be appreciated. Thanks.