It was probably written in the 50's. The central character is the son of a professor in a college town. The Earth passes through the tail of a comet and all machinery stops working. They believe when they are out of the tail the problem will be resolved, but in the meantime the world has to get through a very cold winter without any modern conveniences. My memory of the title is a hazy mixture of 'Night (or Winter) of the Comet' and 'A Fall of Comet Dust'. And no, there are no flesh eating zombies or Triffids in it. I've searched for it on Amazon and asked this question on Askville, no help there.
When you know part of the title of an SF novel or short story, search on ISFDB. Select “Fiction Titles” in the drop-down list and enter “comet”; there are 183 matches. In the advanced search you can restrict the matches to the title type “NOVEL”.
A promising hit is The Year of the Comet (also published as Planet in Peril), by John Christopher, published in 1955. I haven't read it, but the meager amount of information I can find on the web makes me think it's what you're after:
"The Year of the Comet" foresees a world split up, not into States and Kingdoms, but into a business Group. The hero is a scientist with a secret which will give supreme authority to any group in control of it. Inevitably he finds himself the centre of murderous intrigues. In the tradition of H G Wells and Jules Verne.
When Charles Grayner, a dedicated young scientist of the 21st century became employed by one of the great ruling powers, he had no idea that he would hold the key to the future of civilization as we know it.
Sounds like "The Year When Stardust Fell" by Raymond F. Jones, part of the Winston Science Fiction series. Dust from the comet caused moving parts in machinery to fuse together.
The copper-yellow glow of the comet seemed to have brought the whole world to a grinding halt. Airplanes, trains, generators and heavy machinery were immobilized. Finally man was left with only a few primitive tools. In the resulting chaos parts of Mayfield were burned and looted by hunger-crazed mobs that stole and killed as they advanced.