Yep, grounding is strange.  I'd try ungrounding stuff and see if that 
helps.  I was trying one of those clear speech speakers a friend had here 
once and when I hooked it up to my main power supply, I almost blew the 
thing off of the desk when I hit the ptt.  I grabbed a little 12v wall 
wart and used that instead for the speaker, and was clear as a bell.  You 
just have to try stuff.

One trick I saw a ham use years ago, and yes, it does work, for a long 
ground run take a piece of coax using the center conductor for your ground 
wire.  Bypass each end to the braid with a .01 cap.  I don't know why, but 
keeps the ground from radiating as an antenna.
73s
Butch Bussen
wa0vjr