When certain sites load, a popup appears, asking for user name and password. This occurs on MSN's weather site, for example, so it would not be directly related to a suspicious site...unless perhaps it's a side reaction to banners or loggers.
Example: Going to http://weather.msn.com/local.aspx?wealocations=wc:USNY0996
Popup has a pic of one gold key and one silver key on a ring.
Its title bar says:
Connecting to ac2.msn.com
Below, there are edit boxes for entering:
User name: ....
And a checkbox for "Remember my password"
This occurs every time that page is accessed. It does look like the address is a banner or something (not sure what "ac2" is within the MSN.com domain.
I've also seen similar reactions on other sites. Some bring up "bp.specificclick.net" or other domains, though that is not the domain of the page being accessed. The popup itself always looks the same, except for the title bar.
Spybot and MalwareBytes do not find anything.
Any ideas about the cause?