This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.
A 1-bit raster has been loaded onto the geodatabase. An attempt is made to mosaic another 1-bit raster to the same geodatabase. The operation may fail with the following message: "invalid raster data".
This error only occurs when the existing ArcSDE raster is not located at the top of the whole mosaicked extent. The negative extents are being rounded improperly, resulting in an offset that is one pixel short. This causes the data length verification to fail, triggering the error message.