an error code when i terminate bt yahoo

When i terminate bt yahoo I get an error the instruction at 0x073c9017 refrenced memory at 0x073c9017 the memory could not be read yahoo.exe application error could you help me wih this please I changed all hardwre including RAM sticks and CPU and motherboard not made any diffrence phoned BT they do not know I am running AMD processor 64 bit 3300+ and 1 GB memory 2 512 ddram