Connecting the ground wire makes music less lively

Friends,
Lately for some strange reason I heard hum from my TT setup. When I connected the tonearm ground wire to the phono the hum was gone. Thats the good news. The bad news is, when I heard the music with the ground wire connected, it sounded less lively, less palpable. Some vitality was taken away. When I remove the ground wire the life in the music is again back, just that the background hum is audible during silent passages (thats irritating). Has anyone else heard this effect ? Is there a solution to this problem ?

My phono stage is very heavy and can't be moved around. I have to say this problem is quite disturbing because either way there seem to be a serious compromise which is not really the fault of the components.