Hi,
I have about 6 or 8 16GB sand disk 45Mbs cards and 2 32 sandisk 45mbs cards. I have found that I have to install each ML software like it is the very first time performing the install. Start at step #1 and continue on making sure you do not miss a step. I tried just copping the ML files over thinking that would do it being a second card but did not work. The only thing that did work every time was starting from scratch with each card.
I believe that the above should work since you stated that the new cards are the exact same cards, specs etc.
I started by formatting the cards in my camera, etc. I found this procedure easier than using a boot disk utility on my PC. You even have to perform the step that updates the firmware and loads ML on the camera as one of the steps. Remember: I am not talking about the Canon firmware update but the step to select the update firmware option in the camera that loads the ML software into the camera's memory.
John Gerard