[dnanian]

The host volume for the image is mounted by resolving an alias to the file. The system should mount that image, using credentials in your keychain.

Note, though, that Lion sometimes looks for those credentials in the system keychain, rather than your user keychain. If you copy them using Keychain Access, from your login keychain to the system keychain, that may resolve the problem.

But if you have to reboot to get a mount to be recognized, there's something more significant going on - perhaps your mount is failing, or mounting to a different location?