Ken:

I had the same problem when I started milling my strips. I noticed that it seemed to be a function of the direction of the grain. I'll try to explain, but maybe I should post a picture?

1) Let's say that the strip you are milling is being pushed from South to North on your router table.
2) The router bit is on the East side of the strip.
3) The bit rotates from North to South on the side that contacts the strip.
4) The wood grain of the strip is never actually completely parallel to the length of the strip.
5) In order to minimize chipping while routing a cove, the grain should be aligned from North-West to South East, or as near to that direction as it naturally runs.

I know it sounds confusing, but draw it out. Hope that helps a litlle! When I made this change I didn't get any more ruined strips.

-Charlie