I run FS9 since day 1 with a lot of add-ons, and I expereinced almost no CTD. Until Friday last week. FS9 is patched to ver. 9.1, and suddenly FS9 was unable to run anymore, the loading always resulted in a CTD somewhere at the 'loading terrain' stage.I did myself a favor and re-installed the whole machine (XP, FS) - there was already a nice mess especially with FS (though I guess there can never be a 'clean' FS installation if you use add-ons).After having FS9 and some add-ons installed 'cleanly', I tested - and ended in the CTD again.After re-installing FS9 another two times, I narrowed down the problem to the scenery.cfg file.Don't know if any seasonal crashes as in the past have their part in my CTDs (see Jobia's CTD fixes) and whether FSG's American Data terrain.cfg make the situation worse and if applying some modifications to terrain.cfg would help (esp. maskclassmap=0), changing the scenery.cfg in my case works:I suspect the freeware 38m USA terrain mesh 'West Coast' from FS Genesis (available at the Avsim library) to be part of the problem cause.Fact is that if my scenery.cfg is filled with various entries (I sort and order them with a nice scenery configuration program), it can happen that a CTD occurs by simply loading the default situation.Didn't test yet if re-ordering the entries in scenery.cfg would help.But if I delete some entries in scenery.cfg (de-activationg doesn't help at all), the CTD is gone. I don't have the entries anymore, but got rid of the CTD.The last result I found out is that if the West Coast mesh is deleted, CTDs are more unlikely.But I cannot tell that for sure. I found no exact pattern under which circumstances CTDs occur at all. E.g. if I position the plane with scenery.cfg full of entries at LOWI, the sim loads, and I can then 'go to airport' Honolulu (PHNL) without problems.If I load the sim and enter PHNL as the airport on the starting page, the sim crashes to the desktop at about 50% terrain loading.In all cases I have an entry in the event log (though the entry makes no indication where the failure resides).Also checked if some Windows component (service,...) is missing or not running, no success.And, I already made sure not to have 2 AFCADs for the same airport.I'll try now to implement some of the CTD fixes for the 9.0 version, maybe that would help...The bad thing is that now I know that even after taking extreme care of the OS and FS and all installations, CTDs can occur anytime. And since many components change FS core files (tectures, bgls, even cfg files), one can never know exactly what add-on is responsible for a CTD since they heavily interact. The number of possibilities for combinations between add-ons is too big for a normal individual like me to find out where a CTD comes from. I'd need so much time experimenting which I don't have.Sad, but I guess I need to accept the fact that I'll have to live with CTDs from now on...P.S.: I'm currently downloading the whole USA 38m mesh from R. Taburet with wich I'm going to replace the FSG mesh, maybe another light on the horizon...Just my personal story (all that took me 2 days)...Andreas

Hi Andreas,I had the same problem once - the reason was also FSG west Coast.. but that only happened on a certain date (can't remember which) - when I choose a different date, it worked (terrain CTD often is season specific)personally, I think FSG meshes are much better that Taburet (I still remember the fake GAIA)

Been running Raimondo's meshes for a while here( W coast,E coast and Central ) - no problems