Don't know if this will help but I yanked it off of CCO:
"In general, queueing-related features, applied with commands such as random-detect, bandwidth, priority, and fair-queue, apply only in the context of a hierarchical policy with shaping at the parent policy to create a bandwidth-limited traffic stream with queueing of excess packets. In other words, a queueing mechanism applies to packets that have been restrained in a queue by a shaping mechanism. A service policy that specifies queueing and no shaping cannot be applied directly to subinterfaces of any type since subinterfaces do not support inhererently a state of congestion. Instead, you first need to apply shaping to the subinterface using class-based shaping. Cisco IOS Software prints the following log message when an ATM subinterface is configured with a service policy that applies queueing without shaping "
