NRR
Usually, a red cross means corrupt Data. However, you can actually re-catalog the tape by ignoring the catalog that is stored both on you HDD and the tape by going in Backup Exec, Tools - Options - Catalog and remove the tick from "Use storage media based catalogs". However, before you do that, you need to stop the Backup Exec Services and rename the Catalogs folder. Create a new folder named Catalogs and restart the services.
Now run a catalog of the tape. Be aware that this will take about the same time as running the original Backup, as the Data will now be read bit by bit from the tape to create a new catalog.
Tilo