ProblemEdit
Content stored in a BSA is not loading.
Cause - Oblivion cannot find the BSAEdit
Oblivion will not be able to load a BSA that is not registered in the game's configuration file or associated with some plugin. In a more severe case, the game would actually crash as a result.
Solution: See Loading BSAs. In summary: Either register the BSA in the Oblivion.ini or rename the BSA to <some active .esp file (i.e., "DLCShiveringIsles"> - BSA name.bsa).