1) What CPU and GPU temperatures (in C) are reported in SpeedFan or HWINFO64 when your system is idling (no programs running)?
2) What temperatures are reported just before the system crashes? I recommend configuring the temperature monitoring software to LOG temps.
The fact that you can't immediately restart the system does point to a possible overheating issue. If you've already tried blowing out the fan exhausts with compressed gas, a repaste may be in your future. See
http://rog.asus.com/forum/showthread.php?946-G73JH-GPU-Overheating-Observations-and-Suggestions-(Rea...Where did you purchase your laptop? It should still be under warranty since you've had it less than a year. However, I have read reports where certain foreign Service Centers will not perform warranty work on systems purchased in the USA.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT