Thanks for the suggetsion Sue...
“Behind the volume control knob there is a pot switch for the volume control. I have a can of Radio Shack contact/control cleaner and lubricant and sprayed the pot switch. I then turned the volume control on and off several times to lubricate it. It has been working fine every since. I’m thinking that the pot gets dirty and doesn’t make a good contact. Like I said, I had nothing to lose since my speakers were out of warranty. Good luck. I do believe it is a design fault. “
This did resolve the problem. I agree 100% that this is a design flaw, heck my wife's cheap speakers are 10 years old and they work fine and my old Lansings that I replaced with these worked for 10 years as well and no problems with any controls. This is actually my second pair of ProMedia Ultra 2.0 and both pairs died in the same way after one year of service. I don't see how that could be anything but a design flaw!
The speaker do produce great sound so I was glad that your solution worked. I know that design is always a compromise of quality and cost but this time I think the account's had their way.