[ubuntu] Unable to coect to websites, multiple browsers

I'm writing this from FF on the XP partition of this computer. This moing I find that I can't coect, or coection is unreliable, to various websites under my Ubuntu partition ruing 14.04 32bit. All Google related sites, Gmail, Youtube and search engine are inaccessible in Chrome and FF. I could sometimes coect to some websites, Yahoo, e.g., but not others. My access to Google and other sites seems to be fine under XP. I switched out modems, wired only coection, and - thinking that Chrome and FF might be corrupted - installed Epiphany to no avail. I'm at a loss. Any help would be greatly appreciated.