Unable to mount 3D ISOs with double-click but works from system tray

[cyl0n]

I have three 3D Blu-rays that I ripped with AnyDVD HD. They mount fine on my other Windows 7 machine. But my main HTPC comes up with this error when I double-click the ISO - VCMMount Can't Mount %file location%

All non-3D ISOs work.

Right-clicking the Virtual Clone Drive icon and browsing to the ISO works fine. Right-clicking the file and mounting via the context menu fails.

Here are my test cases:
UNC path - Fails
Mapped network drive - Fails
Copying the file locally - Works

So it is a combination of something to do with the file server and the way that the double-click works vs mounting using right-click from the system tray - very weird.