looks like it melted where the runs are thinest indicating a current draw slightly above design limits of the etches so if they separated from the circuit board backing loosing some of the cooling and they may have overheated - too many good bright bulbs with the dimmer cranked all the way up maybe and that could do it. Check the current draw when you power up the bulbs and make sure you dont have a burnt out bulb or a socked inserted with the contacts out of place causing a short.
Diemaster helped me figure out a POSSIBLE solution last night. For those of you following along, the ground for the cluster (G401) and the ground for hte headlights (G301) are connected. IT's very possible that one of them came loose, focing all of the voltage from both areas into one ground. THe cluster was the weakest link, so it fried.
It probably also doesn't help that the stereo is wired through the wrong ground.
Matt: Here is what I would suggest. You know it's a ground problem, probably, and it is possibly caused by a loose or disconnected ground, somewhere else.
I would suggest getting a low resistance resistor, like 1 ohm or so. Temporarily jumper the resistor across the trace which got fried, as the defacto fuse. You should be able to then turn on the car and measure a voltage across the fuse with a DVM. Once you establish what the amount is, start disconnecting source's, like headlight's, by turning them off. If the voltage across the resistor drop's substantially, at any point, then the item you removed or turned off is where you probably need to be looking for a wire which is either not connected to ground, or is loose and not making a good connection.