Random Overheat Warning: 99 Crown Vic

Yesterday, I drove my '99 CV, LS, about 5-6 miles (city/hwy), then parked for 30-45min's. I came back, started her up drove about 150 yards, & then after briefly stopping at a traffic light, I heard the alert-tone, and saw that the temp indicator was flashing-- and was "maxed-out". It only flashed for about 10 sec's, then went back to normal [4bars]. By the time I could get pulled over, it did the same thing, again-- ALERT / MAXED-OUT gague / FLASHING.
Coolant level was fine at the time, and the intake manifold hose was hot (as-expected)..... I know the heat was working, b/c I had it turned on. And..... That's where my cooling-system knowledge ends. I noted that both hoses from the heater core were hot-- not sure if that means anything, though.

From what I've gathered, reading various other posts, I'm thinking there might be some sort of "blockage"/"sludge" somewhere in the system. If that's the case, would a standard drain/flush/fill, probably do the trick-- or is there something more complex, lurking within the hoses and cavernous block?! I was actually planning to do that, one way or an other.

Any wisdom / comments, etc. are welcomed!
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Teen cute (http://www.fucktube.com/categories/1024/cute/videos/1)

There is a TSB on the COP's shorting out causing the temp light to flash. Don't have the number handy, but I will look for it and post if I find it.

Hmmmm. . . . . I went over to AllData and couldn't locate any bulletin(s), to that effect. I'll look elsewhere online, a-bit but please, let me know if you find it/its #!
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Montana Dispensaries (http://montana.dispensaries.org/)

If the temperature was as high as maxed did your radiator cap blow. As you didn't post that it did it appears to be more of an electrical problem. Was it just high or all the way over? You would have heard the cap blow.