It depends on the state of the database corruption as to how much data you will be able to recover.
Is this SQL 2000 or SQL 2005? If it’s SQL 2005 you can do an ALTER DATABASE command and set the database into Emergency mode which will allow you to query as much data as possible. Can you post the exact error message that you are getting?
You can also try doing a DBCC CHECKDB of the database and try and fix the problem.
Is your database in full recovery mode or simple recovery mode? If you are in full recovery mode, and you can fix the database via DBCC CHECKDB you can try to backup the log and then restore the full backup, then roll the log forward until just after the data addition was completed.