It was not an easy one. As you can see from the posting time, I was up late at night. I started by creating new profiles, installing earlier versions, then Safe Mode, to no avail. But, since I could not access any websites, and the problem did not exist with other browsers, I decided to check the Firewall settings. All programs had a green(Allow) or yellow(Ask), for In or Out. Only Seamonkey had reds(Block) for both.
For some reason my ISP mail was being delivered, but Yahoo and AOL were blocked.
I have a hunch of the cause, but I can't prove it, yet.
UserAgent: Mozilla/5.0 (Windows NT 5.1; rv:9.0.1) Gecko/20111221 Firefox/9.0.1 SeaMonkey/2.6.1
A minority may be right, and a majority is always wrong
~ Henrik Ibsen
WinXP, SP3, 512 MB, SM2.17.1, FF21, TB17.O.5, IE8.0, Google Chrome 26, Ghostwall , Kingsoft5.6, JRE1.7_21.