Great - thanks Tim. I'm going to check this out. Sounds like the source of my problem.

>In case you haven't figured it out. The other posters did not mention that
>perhaps you did not set up the SID entry in your tnsnames.ora file.
>
>Run the program "Net 8 Configuration Assistant" and follow the online wizard.
>This configures the client network configuration files that tell the client were the server is...
>
>From experience you should also be able to connect with
>system/manager and no SID....
>
>And if you set up a SID with the "Net 8 Configuration Assistant" you can
>connect with
>system/manager@SID