Did the window you close say "minidump error"? If so then you are using to much ram and should lower the graphics quality (say from highest to high or medium).

Sins is a 32 bit application and therefor uses at most 2gb of RAM.  Once it crosses that, it crashes regardless of how much RAM is available.  And before it get's brought up and I have to hurt someone, using LAA will not work on a 32bit system.  Using it on a 64bit system has seen only very mild improvements from most people, if any at all.  The serious drawback is by using LAA you cannot play online, and as online play is one of the bigger reasons to get the game, it's not recommended to use it.