Sorry to double post, but I've been looking into this problem and it is almost definitely a memory leak, if anyone wanted/needed more evidence.
Using Vista's built-in performance monitor, I recorded stats for the Railroads.exe process and fired up a game. The virtual memory steadily climbed until it hit just around 2GB -- and then blue screened my system. The actual number was 1,970,704,384 bytes, but then again I was only sampling once every 10 seconds so it could have been slightly larger at the time of the crash.
Note that I've tried the editbin.exe hack, am running Vista x64 and have more than 2GB of memory. For whatever reason, the above hack isn't working for Railroads.exe or else it would not crash at the 2GB mark.