97 Grand Prix electrical problem

I have been experiencing an electrical problem for the past six months with my '97 Grand prix GT. I have had it at the dealer for other work and had the electrical system "checked". It comes up as OK.
My problem is that in the process of starting the car, I lose all electrical service. No interior lighting, the clock resets to 1:00, and I can't even remove the key from the ignition switch. The battery is reasonably fresh and the terminals have a dielectric coating and are clean as a whistle...no corrosion. This only happens when starting the vehicle.
The process begins normally. Insert the key , turn it with all the normal sounds, but before it can start, everything dies.
I open the hood, take a 5/16 wrench and loosen the positive battery terminal. I never remove it completely. I get to a point that I tighten the terminal. I can hear relays pulling in. Try to start again and everything is perfectly normal. The quick effortless start reminds me that the battery is strong. It may be several days or a week before the problem occurs again.
One additional point, this scenario is more likely to occur when I have driven several miles or 5-10 minutes, turned to car off to dash into a store or pump gas, and then attempt to continue my errands.
In talking to two service managers, neither has comes across this problem and are only offering 'shotgun" suggestions to correct it. I'm hoping someone out there has something more than a guess.
Thanks in advance. Wib
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I'd be looking at all the gound and battery connections for corrosion or looseness.

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snipped-for-privacy@amtote.com wrote in

either you DO have a bad connection at the battery (B+ / B-) OR you have a bad connection at the power point of the starter solenoid (where the fuse links feed battery power back to the main circuits)....if it were me, next time fault reered its ugly head i would.... 1) not even touch the battery connections!!...2) turn key to run position...3) carefully reach below front exhaust manifold and gingerly wiggle fuse links to see if relays 'pull in' (?, assuming you mean energize)...4) if this caused actions to take place, chase backwards to open circuit (one of the fuse links)...5) if no reaction , start chasing the power or ground down to point of failure (battery cables)............kjun
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