I had this problem for over an year, the hub disconnect for a few minutes and then reconnects.
In the begging it was very seldom, lately is every day around 12-1am. It drives me crazy since NowTV cuts out when I loose connection. I had multiple tickets open and even a engineer at my house. Virgin blames it on work being performed in my area, but for a whole year? I think they are clueless.
When I connect the hub in router mode its stays up longer and does not disconnects that often (maybe once every 3-4 days). I would leave it in router mode but I need to connect my own router (Huawei 635) due to a USB samba server option on my own router.