I've just downloaded SqueezeCenter-7.2.1.dmg onto a PPC Mac running 10.3.9 and double clicked it, I get the 'Verifing...' dialog, but then a 'Warning' pops up: "The following disk image failed to mount - SqueezeCenter-7.2.1.dmg - no mountable file systems"

The latest SP 7.3 universal binary also failed in the same fashon.

Possible lead from Tom: DropDMG’s Get Image Info… command shows that the image uses a GPT partitioning scheme. This is a new disk format that Apple introduced for the Intel Macs, and it’s only supported by Mac OS X 10.4 and later. DropDMG does not use GPT when creating a new image from a file or folder, so my guess is that you created this image by converting an existing image or drive that was already in GPT format.

Quote: Yes, I guess the root problem is that hdiutil’s default settings have changed, and it now uses the GPT partition layout for new blank disk images when you’re running Leopard on an Intel-based Mac. With a PowerPC-based Mac or when using Tiger it does not use GPT.

BTW: SC 7.2 dmg mounts and installs just fine.