If the block belongs to an allocated page, that will cause further corruption.
What's the error on the backups and what does the following return?
DBCC CHECKDB (<Database Name>) WITH NO_INFOMSGS, ALL_ERRORMSGS
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability