I have the same problem. Did you figure out the problem?
I have a 2003 Jeep Grand Cherokee Laredo with 102,500 miles. I bought it new. The battery is less than a year old and I just got a tune up about six weeks ago. Everything that could be checked when hooked up to a computer checked out ok.
For the last month, off and on, while driving at full speed on the interstate, it's started acting like something electrical is shorting out. First it started with the radio "popping" loudly like a short, then the gauges going wild and a few lights on the dash (emerg. brake and abs indicators) coming on and flickering off as the radio cuts in and out. The dash never dims but the mileage indicator numbers flicker as does the lighted buttons on my overhead console, but the digital temperature numbers stay lit the whole time. And my satellite radio (a separate radio) stays on the whole time, not even flickering.
Also, while all of this is happening, the headlights dim, but don't go out. Like I said, this has happened off and on for a few weeks. It will do it on one trip, then not again for a week, then do it a couple of trips, then be fine again for several days.
The engine keeps on purring and doesn't miss a beat. However, it did stall on me once about three weeks ago while I was idleing waiting to pull out onto a road from a parking lot. But then it started right up and hasn't stalled since. Any ideas what could be causing this?