I have tried every suggestion posted on this web site, including the
latest by csj and Robert Ruzback.
It seems that I have two choices: give up on linux or buy a new
computer. Since my computer is less than two years old, I do not plan
to buy a new computer soon.
Redhat and Debian on two separate partitions have the same problem,
they can get connected but do not get onto the internet. As far as I
know, they have only two things in common, the same swap partition and
BIOS. Since I had the same trouble with only one of these operating
systems installed, I doubt that it is the swap partition causing my
problem.
Thanks to all of you who tried to help.