I got my new 7800DXL working first time with Cooperative ADSL, and wifi on all devices (Windows XP; 7; iOS phones; Mac Mavericks). Delighted with coverage to areas that were blackspots with cheaper wifi routers. I made basically no changes to the WiFi admin - wanted to see if it would work with defaults and it seemed to.
But now? Cable connection continues to be fine but WiFi extremely sporadic, with particular difficulty connecting on Windows laptops.
What could have changed? And which settings in this powerhouse should I test first?

Many thanks!
Simon