Also, I can see on my DHCP server logs that the client is sending DHCP requests, and the server receives them. The DHCP server then offers an IP address to the client's MAC, which is when things apparently fall apart. Again, a laptop plugged directly into a Cisco switchport gets an IP correctly, so:
Wired client --> Cisco 3560 --> Nortel 8006 Core --> DHCP server
&
DHCP Server --> Nortel 8006 Core --> Cisco 3560 --> Wired client
Works correctly.
However
Wireless client --> Aruba IAP-105 --> Cisco 3560 ---> Nortel 8006 Core --> DHCP Server
seems to work, but
DHCP Server --> Nortel 8006 Core --> Cisco 3560 --> Aruba IAP-105 --> Wireless Client
does not.
I have tried multiple settings for the switch port that the IAP-105 is connected to, including all variations on 802.1q trunk.
I will continue to investigate this issue, including connecting a wired switch to the Cisco to eliminate some switch-switch configuration/compatibility issue, and trying another Cisco Catalyst 3560 to eliminate any possible hardware/software problems with this particular switch.