RickB, the cracks were real. Colt made a mistake in lighting the frame(that oval cut you see in the rail) which caused binding of the spring, thus the slide beat the frame to death.
The handguns were sent back so Colt could examine and fix them, They did by fixing that weight reducing cut and adding a dual action spring.
The cracking issues are no longer existent.
My point is that the guns with cracked SLIDES were not M45s. Production started months after those pics hit the web, and as you note, and is noted above, the pre-production guns were altered to address the problem. It will be interesting to see if the Rail Gun is modified to more closely match the M45 spec.