I don't have any experience with Laser 128s, but this sounds like a pretty general failure, like the ROM is no longer accessible or something. If this were an Apple II, the fact that you have text at all would indicate to me that the processor is running and the video circuits work, but the processor maybe be just hanging trying to run garbage code. ? Or, perhaps RAM is needed in order to get through startup far enough to beep and something's wrong with the RAM (though I think you can probably make it to the startup beep on the Apple II without functional RAM -- never tried). When I've seen a dead 6502 on an Apple II, it's usually not garbage text on the screen but just a kind of checkerboard, but I suppose that's another possibility (that the 6502 is not starting).
Adam and I taught ourselves how to open the (and more importantly, reassemble!) this system a few weeks ago when we first pulled both of VCFed's out of storage. I suppose it wouldn't hurt* if I open this one and make sure all its chips are seated. * Degnan, that's your prompt to ask "What could possibly go wrong with that plan?"