You might try Root-X (http://www.rootdoctorusa.com/index.html).
I've used it once and it worked although slow-acting. A lot cheaper
than repairing the pipe properly.

Walt wrote:
Apparently my sewer line has a crack about 70 feet out from the house.
Roots are able to get into the line and clogs it up about once a year.
Any one know of fix short of digging up to repair