Since yesterday, my computer has rebooted at random whilst playing Star Trek Online. Sometimes in the middle of battle, opening an inventory screen, changing instances. Sometimes hours into game play, or minutes into logging in. What is odd that the previous 5 days of beta were relatively flawless crash-wise.
However, what I have noticed is that the graphics card seems unusually hot even minutes into playing, which seems odd considering STO isn't exactly a graphically stressing game compared to Crysis or Modern Warfare 2, both of which run without a hitch.
My computer has been running well, drivers are stable, scanned regularly for viruses and malware, has a good-quality power supply (FSP-manufactured Zalman-branded 500W) to power my system, which has an nVidia 8800GT.
If your PC is rebooting while gaming, it is either 1.) overheating and the video card or CPU shuts down, or 2.) you have defective components.
Check system/CPU temps with software such as SpeedFan, and check video card temps with your ATI Catalyst software, or for NVIDIA cards, with your NVIDIA control panel. You can also use third party software to check video card temps.