Acer Aspire 5515 Issue Accessing Internet

We bought the Acer Aspire 5515 computer for my father in law and it worked back in late January accessing the internet wireless in my home (Comcast is my provider). He purchased USB modem so they could hook up their internet provider via the telephone at home (BlueFrog). It indicated that they had a connection, but could not access any sites. So they are visiting this weekend and the same thing is happening connected either directly and wirelessly through my network (either directly or wirelessly the computer indicates the connection is there but when you open internet explorer nothing is accessible).

Any help you be greatly appreciated. Over the phone, Comcast walked through everything and from their perspective everything seemed fine.