No it does not fail. The failure occurs when I load a module that includes "utils" in the resource bundle list. I don't have an application specific resource bundle called "utils", so I assume its either a resource bundle for mx.utils or flash.utils.
I've loaded other modules that don't seem to have "utils" in the resource bundle list. For some reason, that I can't seem to figure out, is why only this module would have a dependency on the "utils" resource bundle. All modules that I have make use of the mx.utils and flash.utils packages.
Sounds like a bug. Please file a bug with a simple test case. I think you need to have Base64Decoder in the module to get it to need the "utils" bundle.
The workaround is probably to put Base64Decoder in the main app.
Flex SDK Developer
Adobe Systems Inc.