After much fiddling with parameters in ArcGIS API for Flex, I have not been able to fix this problem displaying an image service consumed through Flex. My workflow was to create a Raster Catalog, add an imd_date field to the attribute table, and create a referenced mosaic dataset. This had not been able to work properly, apparently since overviews cannot be created for a referenced mosaic dataset.
I found this post: http://goo.gl/xKb8I and my problem was solved.
I love some of the functionality that ESRI provides with many of their products, but often, it’s just terrible working with it.