DBCC UPDATEUSAGE - doesn't that only have to be run on SQL 2000 or upon upgrade from 2000 -> 2005?
I thought the issue had been corrected in 2005 onwards?
DBCC UPDATEUSAGE BOL quote:
"In SQL Server 2005, these values are always maintained correctly. Databases created on SQL Server 2005 should never experience incorrect counts, however, databases upgraded to SQL Server 2005 may contain invalid counts."
As I mentioned before, using sys.dm_db_partition_stats is the most reliable, future-proof method.