Some BIL, BSP, BSQ files do not display in ArcGIS 9.2 or a later version. In particular, 1-, 2-, and 4-bit BIL, BIP, and BSQ files are not displaying. Other bit depths for these formats are working fine. As well, other file formats that have 1-, 2-, or 4-bit pixel depths are working fine.
Since ArcGIS 9.2, ESRI is using a new format library to read certain formats, such as BIL, BIP, and BSQ, however this library does not support 1-, 2-, or 4-bit depths.