Linux – Unable to mount volume, an operation is already pending (with multiple users)

I'm running Linux Mint 14 – pretty much whatever the default install settings are. When I have multiple users logged in and I plug in a flash drive, or digital camera, or any other USB storage, rather than popping up the automount, it does nothing.

So if I use Caja (I guess the Nautilus equivalent) an try to mount it, it tells me:

If I log into the other user account I see a window asking me what action I'd like to take.

How can I turn off automount, and have it only try mounting when I click on it from within my file browser?