If the error is that you're out of space in the transaction log you can truncate the log using:
DUMP TRANSACTION databasename WITH NO_LOG -- SQL 6.5/7.0
Or
BACKUP TRANSACTION databasename WITH NO_LOG -- SQL 7.0 Only
If no space is being freed, check to see if there's an open transaction:
DBCC OPENTRAN(databasename)
You will not be able to truncate the log past an open transaction.
HTH
-Mike