It turns out it was a driver problem.
Although I had the newest wi-fi driver installed from the Lenovo site, i found a newer one on the Intel site, just a couple days old, installed the new one, and now no more problems with connecting to the Internet from the adhoc connection.
Still one minor problem though. Every single time I connect to the adhoc network I am asked for the WEP password? Why isn't it remembered, and why does the network not connect automatically as I set it? (It connects automatically to that network, remembering the password, on my WinXP and Win7 computers, and even my Idevices, but not from this Win8 computer.) (The Win8 computer will connect automatically, remembering the password, to normal access point networks though.) Will Win8 not connect automatically, and not remember the password, for an adhoc network? Or another problem with the driver or Intel software? Anything I could do to fix that?