Line fault at the outlet -- do I need an electrician?

Yesterday, I got a Panamax, Max 1500 surge protector and line conditioner. (I got a very good deal on it, and am just trying it out.)

I plugged it into an outlet I've been using for a while and one of the red lights on the front lit up saying "line fault." (I'm not sure how this is different from a "ground fault." Maybe it's the same.) The Panamax does not do this with other outlets in the room. They seem ok.

So, I know this means that the outlet is improperly wired. My question is, might this be a simple thing to check and/or fix? Any suggestions most appreciated. It's the only outlet I can use to have my audio set up where I usually have it. Now is not an optimal time to call an electrician. If this is a big problem, I'll try out my gear somewhere else in the room, but if I can fix this without too much expertise, that would be ideal.
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It seems to me that someone used a 30 amp cable to feed two 15 amp circuits. There must be a junction box where the orange cable branches off to two 15 amp cables. You should get an electrician to check it out. You are better off playin' it safe!
A subpanel is a panel fed from another panel.

Like in my old house I had a 200 A main panel, but a sub panel in my workshop. The physical size isn’t the determining factor. What makes a sub panel a subpanel is that there’s another breaker in the house which controls all power to it.

The 200A main panel (techincally service panel) fed a subpanel via a 60 AMP breaker. That subpanel had 4 other breakers.
If your house has aluminum wiring, (or not?), you should try unscrewing the outlet (with the breaker off), then remove the wires, and tighten them to the screws, not the push in inserts.  To remove inserted wires, push a very skinny screwdriver into the little slot by the wire.  Corrosion can be defeated this way, especially on aluminum wiring.