it seems like its a driver problem then, have u updated everything? Cuz usually when the game crashes, its the graphics card giving a problem. If it freezes/hangs, then i would say temperatures. As for overclocking, u would only really need to do that only if ur processor is the bottleneck for gaming performance. This is however if u only use ur computer for gaming and regular uses. If you are doing mad calculations like the Overclock.net's folding team, then u would want to push the processor to the brim.
and to note if you do intend to overclock ur processor, please PLEASE keep in mind that 99.9% of all brisbane cores have faulty temperature sensors. For example when mine is at 20C its actually at 40C and so forth. And lastly unless u have crazy cooling, brisbanes will hit around 3.4ghz-3.6ghz.
So good luck and i hope to hear about ur progress,
S1L3Nt