newbie - Oracle Workgroup server connection

When trying to connect to the Oracle Workgroup server (7.3.2.3) using the 'test' of:

    sqlplus scott/tiger_at_XXXX (where XXXX is my db id)

I get the following error:

ERROR: ORA-01034: ORACLE not available
ORA-07429: smsgsg: shmget() failed to get segment. SVR4 Error: 2: No such file or directory

I've checked all of the permissions, and verified the consistency in tnsnames.ora and listener.ora

What else is there?

Incidentally, I can log into the database using the system login from the web front end, but I can't get to it from sqlplus.

• Grace