HAI Omni II and X-10

Looking for some insight here. X-10 was working, now its not. I get mixed results across the board. It did work previously through PCAccess and HAI control panels. Now it will not. I can use a remote and sometimes the lights will respond, sometime they will not. I have no flourescent lighting. I wired a coupler at the electrical panel. Obviously there is some interference causing the problem. What steps should I take to resolve it? I have a big investment in Leviton lighting. My first thought was to get another coupler, one I could plug in in the wash room. Also, I thought about getting a booster link to boost the X-10 signal. How about filters? Do they work? I hate to buy one for every PC I have (8 of them) and AV equipment. What do you recommend? What works? What step should I take first?
I'd recommend using a test meter to see what's happening. Could be the the coupler isn't working. Could be that you need a coupler repeater. Could be noise. etc

There are a lot of could bes. Testing would be the best way to find out. We do have free loaner test meters available.