As I think I've mentioned before:
When TalkTalk finally gave me VDSL, I bought a new router, Netgear 7000 Night-thingie. It worked brilliantly with ADSL, but swapped it over and it simply refused to connect to VDSL. It should have done. I plugged in, after much frustration, put in the cheapo TalkTalk router they gave me and it worked instantly. Bugger.
But lately I've been having to reset that router at the mains when the line drops. Daily. Or twice daily. Or every two days.
Had another go this afternoon with the Netgear. Failed, same problem: wrong username and/or password. It isn't wrong.
So now I'm back with the Talktalk unit.