I've been playing since the first MTW and I've been on this site for ages - even was an assistant mod in the Tavern GAH.
Here are the top two causes of bugs in MTW:
1) Not enough system resources/system not good enough. These games are system hogs. If you don't have stuff, the game will invariably crash.
2) Plenty of system resources but your computer has viruses, old file fragments, or weird stuff going on with the file structure that all lead to overuse of what would normally be ample system resources.
Just my two cents.
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