NO Power at ALL!?

This is a real head scratcher...atleast for me, otherwise I wouldn't be here. But anyway, I have a 94 Hyundai Excel that is getting no power at all. No dome light, none of the internal lights or external lights. I have had the battery checked and all is good, battery cables look good, fuses are all okay...I just don't know whatelse it could be. Could it be that the ECM is bad? I told a mechanic what was wrong and he said it could possibly be my ignition switch. Sooooo I go and buy one and install it. Guess what, it didn't fix the problem! I have searched all over the net and have found nothing with this sort of problem. Can somebody help please!?!? Car was working fine before, I was running around all day and then it just wouldn't start. I had power then, but the starter wouldn't kick over. All I could hear is the solenoid click, then I waited all little while and tried it again, but this time no power, just dead. ????????

Possible problems :

- Ground issue
- Main fuse link (a big 100 AMP fuse hidden somwhere under the hood)
- Starter
- Main harness

The ECU would let you have lights and acc. but what I just mentionned could cause the car not to start AND not having any power at all. Hope it helps.