Ok I've tried the recommendation and no luck. Here's what I did:
I changed the DIR-655 Router IP Address to 192.168.1.21, disabled DHCP and rebooted. I could not get any Internet or connection to the UStec router once I changed the DIR-655 IP. I forgot and later changed the Internet Settings in the DIR-655 so that the WAN pointed to the UStec gateway @ 192.168.1.1 - changed the Connection Type to "Static" and received an error when trying to save the configuration.
Here's the error message I received when trying to save the configuration:
"The addressing of the Internet side learnt thru DHCP conflicts with the addressing selected for the LAN side. Internet communications will be disabled until you have changed the LAN side addressing to resolve the problem."
I then changed the DIR-655 Router IP back to default (192.168.0.1) with the WAN pointing to the UStec gateway but after reboot, I found I could no longer connect to the DIR-655 GUI. I had to manually reset the router to connect to it again.
Unfortunately from the UStec side, I couldn't assign a static IP to the DIR-655 but figured the DIR-655 would pickup whatever IP I gave it.
Here's my DIR-655 version:
Firmware Version: 1.11
Hardware Version: A2
Unless I missed something, maybe you can't use the DIR-655 as an Access Point with another router? Any ideas anyone? Can anyone from D-Link confirm or know how to configure this?