PowerConnect switches have IVL (independent vlan learning).   This means that the same mac can be in different vlans.   In other words, the vlan is part of the address lookup. 

Thanks, BH.  Is the IVL a feature of all of 27xx, 35xx, 53xx, 54xx, 62xx?

yes

Thanks. 

If a General Mode port receives an untagged frame, and the destination MAC exists on two different vlans, then I think that the switch would not know where to send the frame:

1. interface g1, mode General, pvid 100, add vlan 300,500 untagged
2. interface range g(3-4) mode General, pvid 300, add vlan 100,300 untagged
3. interface range g(5-6) mode General, pvid 500, add vlan 100,500 untagged
4. MAC 00-00-0c-07-ac-01 is on both ports g3 (vlan 300) and g5 (vlan 500)
5. device on General Mode port g1 sends an untagged frame to 00-00-0c-07-ac-01

The Dell would receive the frame from port g1, and see the destination MAC on two different VLANs; port g1 has permissions to send to both VLANs.

To avoid this situation, should I avoid using General Mode at all on any switch that also may see the same MAC in different Access/Trunk VLANs (e.g.: does enabling general mode on port 1 somehow affect IVL for other non-General-Mode ports); or is it sufficient to only ensure that the duplicate MACs are never used on General Mode ports?

PowerConnect switches are IVL switches (independent vlan learning).  This means that the vlan is used in the destination port lookup.  In your example, in means that the same MAC address can exist in multiple vlans.