Bad Ram?

hey guys I keep getting this error when I put my computer under heavy load with certain games this is the error:

hl2.exe - Application Error

The instruction at "0x2418a389" referenced memory at "0x0d7bb138". The memory
could not be "read".

Click on OK to terminate the program        this error happened in Half life 2


Could this be Bad Ram? I have 1GB of corsair ram, two 512's of PC2700(166MHz).

Is it always the same address?

If it is, then probablly its the ram.  Else, something is causing the ram to fail. What wattage is your power supply?