Ground Loop - New Twist?

In a recent discussion I pointed out having lost a 60Hz speaker hum from my stereo after moving to a place with a better electrical system. Well, that claim was premature. The cable company was out yesterday, did their thing and OUCH! things are worse than ever. With the TV and digital cable box in the loop the 60Hz hum is LOUD. Putting a ground isolator on the cable connection helped, but doesn't completely remove the noise. The installer tried to ignore the problem, even said it is normal, but finally relented after much insistence on my behalf, called his supervisor and a technician is supposed to be assigned to investigate the problem. What I'm hoping for with this post is a little guidance on the best path(s) to take when the technician comes out.

Before the cable installation there was a *minor* speaker hum audible from a couple of inches away. It was about as loud as the tube rush from the pre-. Floating the ground on the amp or pre- does remove it. With the pre-'s ground floated there is a lack of life to the sound, so that isn't an acceptable fix. I tried floating the amp's ground this morning, against my better judgement, and while the hum is gone this is really not my preference. Too unsafe; the ground is there for a reason.

In conjunction with this the ballasts for the flourescent lights in my office and garage all started buzzing, too, right after the installation. Something is plain not right.

The installer said the cable connection is grounded to "the power mass". This was not a familiar term, so had him show me the ground connection. It is attached to the outside of the breaker box next to the power meter. Somehow that doesn't seem right.

What are the available options and what should I say to the tech to get this fixed? BTW, I do have a basic understanding of what causes ground loops. Also, the equipment is a McCormack DNA-1 and the pre- is a Sonic Frontiers Line 1. Thanks in advance for walking me through this one.