I am having trouble installing the latest production build on OS X. Running 10.7.5. When I try to mount the dmg it fails with a “no mountable file systems” error.

Researching that error someone suggested a possible download error. I downloaded the image again, same result. The checksums also don't match.

Build 13.0.509 works and I am fine with that version.

I just thought that I would a) see if others have a similar issue and b) get more education if someone is familiar with this issue and a solution.

Sure sounds like an incomplete or interrupted file download. See if you can run an image verification in Disk Utility, or try downloading using a different browser. Using OS X 10.7 shouldn't be an issue.

On OS X 10.9.4, the checksums don't match either, but the image mounts without any problems.