Update: Thanks to this post and some fiddling around my firewalls I figured this out. Thought I should post it in case anyone else has had the same dropping to desk as I did.
Have you installed anything recently?
If the game is still running and you can alt tab back to it or choose it from the task bar, then this is a background app that is throwing itself to the fore and displacing the game. Google Clean Boot and your OS to see if a Clean Boot stops this from happening. If it does, then find the offending app and do something about it.
I am running Win 7 firewall, also AVG AV ...I found that AVG kept disabling my Win Firewall , while using it's own firewall. Problem with that is AVG logs an alert something like 10-11 times a day ( at least) . I found out it was dropping to desk everytime "Akami Net Sessions" , accessed to internet and AVG would try to block it. Weird. I disabled Akami and set it to ask me when it needs to be enabled to update whatever it wants to update. ( usually Adobe or if you check it out...this program talks to the net to update all sorts of programs) Though this never posed any problem ever before....maybe it can be exploited or hacked?
I was then down to just 1, maybe 2 desk crashes during 1-2 plus hour playtime...and usually just right at the start. I figured out that every time i started my system up fresh, AVG AV would disable windows firewall again on a fresh boot. I finally just disabled AVG 's firewall, and enabled Win 7 firewall. Everything works perfect.
Two thoughts though, First,I have to deal with AVG annoyingly telling me that my system is unprotected because the FW is disabled. ( You would think it could notice that the Win 7 FW is on). And second, was my Akami Net Sessions hacked or something? Because I played the game from release until the last week of Jan before experiencing these desktop crashes. Over 200 hours of game play.
Thanks again to the all your answers and to the above Mod for leading in the right direction
