Vince, I feel your pain. Another local ham and I have had the same problem. Yes, it's Powerline noise!. I have a 756PRO and my display is was EXACTLY the same as yours. I made a couple of Kent Brittan's "cheap yagis" and went searching with my Icom R10 receiver. Since the yagis are made with thin welding rod and 3/4" PVC, they weigh next to nothing. I made a 3 element one for 136 mHz and a 9 element one for 435 mHz. The 136 will get you in the right direction and the 435 one is sharp enough to point right to the top of the pole and at a bad lightning arrestor.
Florida Power and Light are just wonderful people. They will go waaaay beyond the normal Utility Company response. They just LOVE it when I identify the pole and put an orange ribbon on it, so the crew doesn't have to screw around 'looking' for the problem.
Don't get me wrong, FPL has all the state-of-the-art gear, but if I can save them a day or two of looking, they really appreciate it.
The ARRL has a great book on 'noise'. I regretfully say I have learned a LOT more than I ever wanted to on the subject of Powerline noise, but you gotta keep working at it.
Oh, I am the last person on my distribution line. Unfortunatly, we have had some wicked lightning storms here lately, so it's just patch, patch, patch.
Don't dispair! It CAN be fixed!!!
Contact me off the list if you need advise....