Cisco Switching/Routing :: 3750G Access Layer Mac Flapping

Lately I have been noticing mac flap messages on some of our access layer 3750G switches. Just a little background on how this is setup.
 
These 3750G switches are stacked and uplinked to a distribution layer 3750E stack (2 switches) via cross stacked etherchannel. (Usually 4 links) The access layer switches are stricly layer 2 where the distribution layer 3750E is routing the VLANs at the access layer to to the core 6500 switches.
 
I have just about ruled out physical loops on these stacks for the reason that the Macs are flapping. I am seeing this on two different stacks now each having 3 switches in the stack at the access layer. The cross stack etherchannel is spanned across the first two switches at the access layer and connected to both switches at the distribution layer. I have checked the etherchannel status and all ports appear to be part of the etherchannel and they appear fine.
 
The mac addressses that are flapping are just plain old desktop machines that plug directly into the access layer. I usually see this when the mac is learned on a port such as when a machine is plugged into the network or reboots.