Lion won't mount any disk images with the built-in utility or Disk Utility

Having the same problem. Just getting a warning, 'no mountable file systems'. Tried with Silverlight (for Netflix) and Adobe flash dmgs, won't mount. I did finally get the Silverlight to mount somehow using 'Disk Utility'. Hoping for an answer soon.

I have this problem with MySQL 5.1.34 and 10.7. According to this page it's because the disk image is using UFS as its filesystem:

http://forums.mysql.com/read.php?11,278794,278794#msg-278794

Switching the boot mode of Core-iX machines to 32-bit mode helped with this problem under 10.6.x, but it doesn't seem to help under 10.7. This is a big problem for me at my work, because we rely on both MySQL 5.1.34 and Apple computers for one of our core products.

Cross-referencing another post because I think it may be related:

https://discussions.apple.com/thread/3191735

I'm seeing this, too, on a new MacBook Pro that came with Lion pre-installed by Apple. I don't know the cause, but one workaround is to open the .dmg file on a different machine, then copy over the contents (installer or application) to the Lion machine. Tedious, to be sure, but at least it lets you get some software installed.

Update: I saw another thread that had mentioned a problem with this while running Migration Assistant. I wasn't running it, but had started it earlier, and then quit out of it, and hadn't yet rebooted. After rebooting, I am now able to mount disk images that wouldn't mount before. So maybe just a reboot could fix it? I'll update here if the problem returns.

elnj, sounds good... very curious to hear any further info you uncover.

Unfortunately copying the contents of the disk image won't work for us as our customers have to download MySQL and install it, and we can't assume they have another machine (nor do we want to shift that burden onto every customer). Repackaging MySQL 5.1.34 in a Lion-compatible .dmg is a simple operation but legally we are not allowed to redistribute it.

We ended up validating a more recent version of MySQL (5.1.46) which does not have the mounting issue under 10.7 and also mounts just fine under 10.5 and 10.6 as well, regardless of the bit-ness the machine is booted into.