Cannot mount a .dmg file

Try testing the file using "Disk Utility". Open Disk Utility and from the "Images" menu run the "Verify" option. If things check out but you still cannot mount the image, copy it (so you have a backup) and try to use that same menu to convert it to a different format. Perhaps that will enable it to mount.

That means that perhaps the file you downloaded got a little messed up on its way to your computer, or perhaps the checksum information wasnt included in the original file. Disk images have checksums to ensure the integrity of the disk image is ok. It works by summing up the number of bits and bytes in the image/file according to a summation algorithm that will give you a specific "checksum" number. The file should contain the checksum number (created and embedded in the file when the original disk image was created) that your computer compares to it's checksum number that it gets when it runs the same algorithm upon mounting the disk image. If the image is intact, then the checksums will match, but if the original checksum is missing or they dont match, then the disk will be avoided for fear of corrupt data, etc.

I'd recommend re-downloading the file, but if you want to try one more thing with this one, open "Disk Utility" and in the preferences uncheck the "Verify checksum" option. Then go to the file menu and select the option to open a disk image and hope it mounts without checksum verification. If it's just a checksum error where the checksum number is missing, then the contents should be fine and you should be able to install the program, but if there's a problem with the disk image then its likely the installer files will be corrupted and you will get errors. Its worth a shot...

Message was edited by: Topher Kessler

Looks like you've got yourself a corrupt DMG file that you need to re-download. More often this is the case than not with checksum errors. It could have been corrupted in your download, or the copy on the server could be corrupted. Either way you'll need to get another, functional copy from the company. Let them know the disk image's filesystem is corrupted and will not mount after you've run several tests on it using "Disk Utility" so they're aware its a problem with the file and not something on your end.

If you can copy it from him then do that. It sounds like the file is getting corrupted in transit to your computer. If his copy still wont open then try burning his copy to a CD so nothing can change it on its way to your computer, just in case its some funky networking software configuration that's causing the problem with this particular file.