DGND3700 - Regular Disconnects

Hi, Newbie here. I replaced ol' trusty DG834 for a DGND3700 and since install, its been a bit hit and miss. Worst bug-bear is that when the Xbox (wireless) is turned off, so is the wireless connex for everything else, ie Netbook and laptops. Also happens when a landline call is terminated. The new router is in the same place with the set-up (ie PC's, printer etc) as the old DG834 with the same filter. I used the Wizard for the settings on normal talktalk broadband line ..any ideas would be apreciated. As you can guess the missus is a bit peeved that this doesn't work as well as the old'un..

Thanks