fsx crashes on 8.1

ok so my i just upgraded my desktop from win 7 - win 8.1 ( gaming reasons) my fsx crashes it doesnt happen on win 7. ok so here's what happened:

1st flight: RPLL - OMDB

so before approach i want to see dubai clearly so i've changed the time then after 1-3 mins my sim crash.

2nd flight : RPLL - OMDB

same step to make sure that it's just not a glitch. it crashes again

3rd flight : RPLL - OMDB

this time i didnt change the time. it didn't crash wow.

4th flight:

same step. it didn't crash 

5th flight ( w/ sim rate )

same step as 1st - 2nd flight. well it crash

6th flight (w/ sim rate )

same step as 3rd - 4th. i didnt crash.

so guys any idea why is it happening on 8.1 i've done this steps on win 7 many times but my sim didn't crash/