Although it's my favourite steam loco, could we know your proper name, please ?
Sorry, but I don't have an answer to your problem - does the route run its activities correctly?
My experience with trying to run the Activity Editor on the as-supplied T-M route is that it takes a very, very long time to start up. In fact, it shows as "Not responding". Using TrainStore to select just one activity results in AE starting almost instantly, but this is not a lot of use if you want to create an activity as the only stock available will be that used in the selected activity.
A better option, if you want to create activities in T-M is to use the Mini Loader (please come back if you need more details). Similarly to TrainStore, with Mini Loader, a single activity is selected, but the stock items are not hidden; the downside is that all the consists, except those used in the activity, are "disabled", so not available.
The "stopped working" message is, very often, associated with the location of the MSTS installation - if it's in C:\Program Files or C:\Program Files (x86), you should uninstall it and re-install according to the Steam4Me tutorial : http://msts.steam4me.net/tutorials/inst ... ts_w7.html
It might help if you could post your PC specifications, in particular, the graphics card.
Intel i5-4690K (3.5Ghz), Gigabyte GA-Z97P-D3 m/b, 8GB DDR3 RAM, NVIDIA GTX 750ti (2GB) graphics card, Asus Xonar DS sound card. Win 7 Pro 64 bit.