Cannot connect to Wifi after 7PM every day!

I'm facing a very strange problem since the day I installed my service.
I have a HITRON BVW-3653 and the Wireless connection drops every day around 7 o'clock in the evening and I'm unable to reconnect to the network. It shows up in the 'available networks' list
in my device (PC, phone, tablet PC) but when i try to connect to it, it always disconnects. The internet is fine because when i connect the PC via ethernet cable it works fine.
It works great all day but around 7 EVERY day I have the same problem with all my devices.
When i reset the modem nothing happens. I even factory-resetted and still nothing. I changed the SSID also to no avail.

Any ideas on what it could be?

many thanks

see page 65. if it isn't that, I don't see any other candidates

http://www.lumieretv.com/assets/main...m%20Hitron.pdf