work-around for network woes

So, I can't log into my bank from my new Mac (but can from old) on my comcast internet service. We knew this already. So I tried something this morning: I've got my verizon 3G Ipad tethered to my Mac via USB. Bank works. LJ works. So I'm not a very technical nuts and bolts network geek, but I'm betting that this is some really obscure strange thing that causes only 2 of the websites that I want to access not do passworded things properly.