In the past, two genvibers have blown that fuse by crossing the wires when trying to jumpstart somethingAlso, johnsoax blew the 100A fuse shorting something out while messing with the alternator. The 100A fuse is bolted into the underhood fuse block, and in such a way that you have to move the fuse block around to get to it. He has some pictures and discussion about replacing it in
http://forums.genvibe.com/zerothread?id=16307 that will help.Still, that's a symptom, no idea what would have shorted to blow a 100A fuse while you were just driving along but it's something you want to try to find. If you buy a replacement, might be worth buying a spare until you know for sure whatever shorted out won't do it again..