Make sure your the offset is zero on your 4100. You'll have to get out of AP mode because you can't set the offset while in that modem.
After you return to normal mode, you shouldn't be in DR mode, but your 4100 should display the frequency and indicate that you are in DV mode. Then, enter the menu and select the top menu item, "DUP/TONE", then select the Offset menu and set it to zero.
Tom Early