Troubleshooting

Enterprise Manager: Cannot edit this cell
Solution: try change using UPDATE command

Troubleshooting and Fixing SQL Server Page Level Corruption

Issue:
Extent in database is marked allocated in the GAM, but no SGAM or IAM has allocated it
CHECKDB found 1 allocation errors and 0 consistency errors not associated with any single object.
Opinion 1:
This is one of the few cases where, even though repair allow data loss is required, there probably won't be data loss. It's errors in the allocation structures and checkDB will repair it entirely.
(source: DBCC CHECKDB with allocation error)
Opinion 2 (in sync with #1):
you have corruption not associated with any table
(source: How do I fix Damaged allocation pages)
To repair:
DBCC CHECKDB ('xxx', REPAIR_ALLOW_DATA_LOSS)

Verifying backup files

How to Recover MSSQL from "Suspect Mode" / "Emergency Mode" / "Error 1813"