I tried connecting the grounding wire to the grounding post of my outlet, but the problem is still there. Literally, I grounded my turntable like I would ground any other device that needs to be grounded.

Having this, I begin to think that the problem is really "Either in the wiring between components or in the grounding scheme coming off the wall." as you said.

Tomorrow, I am going to check the inside of my turntable and if everything appears to be fine, then I will have talk to my building's superintendent about the faulty outlets...

Thanks for keeping in touch!