You need to run a complete check on the db:
SELECT DB_NAME(5) --this is the "problem_db"
DBCC CHECKDB (5) WITH PHYSICAL_ONLY /at first, at least, just run a physical check/
Specifically for your current error, determine which object it affects. If it's only a nonclus index(es) -- that is, the index number is greater than 1 -- you can script out that index(es), drop it(them), then recreate it(them).
SELECT OBJECT_NAME(p.object_id) AS object_name, p.index_id
FROM sys.allocation_units au
INNER JOIN sys.partitions p ON p.partition_id = au.container_id
WHERE au.allocation_unit_id IN (72057594060931072, 281474980249600)