Just when I thought it was stable. . .

Ever since my major re-build and upgrade of my computer, I have had two months of wonderful route building and game play with little or no problems, even running 14 AI trains at one time in my custom route, which has grown to 50 miles in length. All was wonderful until last night. For some unknown reason, now when I click on the Scenerio Editor button, I get the "something bad has happened" error. All of the payware routes run fine. The problem is with my custom route. I've tried all the usual things. Can anyone suggest to me a cause/solution for this problem??? At this posting, I have 2,319 hours into this route. Someone please tell me I haven't lost it all because re-building the KCS from Blanchard, Louisiana to Minden, Louisiana through Shreveport is a major operation. 
