There can be a number of reasons for the game "crashing". One is aircraft spawning which are not fully set up to appear in the CFS3 world. They may be missing a sound file, weapon, pylon or whatever. Are your spawns era specific or are you in random spawn mode?
I use cagen 1-2.xls to check all aircraft in an install (available for download here at SOH IIRC). For ETO it is a big job for the CPU to churn through all the loadouts, etc. However it identifies a few aircraft which are missing pylons or weapons. The other way to check aircraft is to manually go through each loadout in the QC UI. That is a slow job in ETO. Once you have selected a loadout for an aircraft which calls for a missing pylon/weapon, the game will crash. Using the cagen.xls is much more efficient.
Once all the aircraft are checked, it might be something else, but I suspect a lot of the crashes are aircraft related. Another possible cause of CTDs is tweaks to config which are too optimistic and your memory or whatever gets overloaded with all the eye-candy. People all have their own pet theories for CTDs I suspect.
HTH,