Can't start PBEM game after Blue Marble install

I installed BMT just the other day and things have been running just fine in my single player game. Today my brother finally emailed me back the turn in our PBEM game. When I tried to load the game, I got the following message:

"The save file you have selected is protected to ensure that the assets in your mod folder have not been changed."

It just gives me an 'OK' box to click on, and when I do the game exits and I can't start my turn.
I even ran the Uninstall within BM and tried again and got the same error. What's going on and how do I fix it?

All is solved now. It wasn't the BMT itself that caused my problem. It was that I had used the scaling tool to change the size of the city display. Just need to restore the defaults before loading the PBEM game.