Your digital gear is telling you that you did something that was not kosher. By lifting ground you are depending on the connection between neutral and earth ground all the way back at the box. IF there is resistance between earth and neutral because of a long run of house wiring anything can happen. The best thing to do is to use the cheater plugs and tie the grounds of all the equipment together at one point and then to your outlet's ground. BTW a good test to see if your outlet is wired correctly and that neutral and ground are connected well at the box is to measure the AC voltage between Neutral and Ground under load. It should be close to Zero volts. If it is not zero either your ground or neutral has some resistance and should be looked into.
Weird Thing after I lift my ground.
I've finished lifting grounds on my system by buying 3 cheater plugs for my A/V pream, CD-Transport, and DAC. During the process of lifting grounds I switched everything off and unplugged everything from outlet. After that I plugged everything in the same place except those three units that I plugged them through cheater plugs. Now I see the weird thing. Whenever I stop CD-Transport or switch it into the standby mode, the "signal lock" LED of my DAC always blinking like it's trying to lock the signal. If anyone has experience this kind of situation or can explain this situation, I'm really appreciate.