I have tried some much of what has been suggested, Also started up from a new account with fresh preferences, I deleted
/Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist
/Users/[username]/Library/Preferences/com.apple.systemuiserver.plist, unplugged everything except keyboard and mouse from the imac and zapped the pram, connected directly to the computer and totally bypassed the Airport Extreme, and some other stuff i can't remember. It makes me think it is either something in my computer or Comcast. Why I lean toward Comcast is normally this is not a problem, but about every year and one half this shows up for about 3 weeks and then self corrects. 3 years ago when it happened I went to a local authorized Apple repair shop and they tested the machine for 24 hours and could find nothing with their diagnostics. One week later it was fine. Also one year ago it was doing this a finally a tech who came to the house told me it was because they were changing the area so it could use comcast telephone. Two weeks later all was well. This winter had very, very slow service and after various tech house calls, they announced that they had a bad line for the area, plus other lines just outside the area, plus they had to reconfigure something at the home office. Anyway all was fine until this last go round. (I must say the techs who came to the house were great) So there was also some other non sleep weeks. Anyway most of the time all is well except for the moments.
Anyway thanks for the advice and info to all who responded. I have basic Mac Software, MS Word FM Pro, Quicken and some other not very complex software. I even turned off all the check for update software preferences. So I will call Comcast now. They always want me to get a new modem, which I did twice and it didn't work, and hopefully I can get an answer from them or Apple. As a P.S., I have found the support people on the phone have no idea what the techs who come to your house are doing. When I try to get one of the outside people to talk to, it is almost impossible. For example they didn't know the techs were working on a problem in the area or setting up phone service. This is also a problem i have had with TV issues, where finally the person who came to the house after a few calls said the problem is not with you but in other work we are doing. I also will repeat all tech phone and house calls were very polite and nice people.
