I've been having this happening off and on with disk images (encrypted and non) since 10.6 came out. Things improved somewhat with 10.6.4 but I'm still about 50/50 for dmg's getting a generic icon when they mount. (and the get info shows them, and when you eject them, the icon briefly shows before it blips off the desktop.... weird) Is this what you're seeing?
I work for the Department of Redundancy Department
