If by "vibration" I think I understand that you feel an electrical "buzz" when touching the metal trim around the keys on the keyboard? Yes, I have felt that too, especially when my G74 was new : touching the metal with a slightly wet finger or something there was a buzzing sensation, especially when moving the finger around. It was noticeable for some time, but lately (last month or two) it has gone away. I believe I remember reading that the touchpad on the G74 is grounded improperly to the metal keyboard trim with tape, which is why it has given so many people issues. I'm not sure if this was the source and the tape under there has fallen off or something, but I don't feel the "charge" anymore. I just put a multimetre on the metal and don't measure anything about a few millivolts now, but I'm sure it was probably a few volts when it was charged.
Anyhow, I'm sorry: I never did solve this. But it seems to have disappeared: hopefully yours will too.
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G74SX-CST1-CBIL, i7 2630QM 2GHz
32GB DDR3 RAM @1333MHz
GTX560M 3GB DDR5 (192 bit)
17.3" LED 1920x1080
Sentelic TP, BIOS 203
Debian Linux Wheezy (Testing) Kernel 3.2, NVIDIA 295.40