GN-BR01G Router

[RonH]

Has anyone experience of Windows Security pop-ups that give the following message:

The server xxxxx at GN-BR01G requires a User Name and Password

The layout of the pop-up is very similar to the pop-up you get when you log into the Router to configure it.
xxxx relates to various pop-ups that have occurred over past weeks including those from:
4.bp.blogspot.com
cbk2.google.com
Google Analytics
i4.ytimg
mt1.googleapis
server.maps.google.com

I have factory reset the router a couple of times and changed paswords etc in case of some security attack. I use the router for two pc's and both experience these pop-ups at random times. System scans do not show any malware and I do not actually get 'redirected' so I don't think it is a DNS Changer Trojan ... the online 'test' also shows my pc's to be clean.