For what it's worth, I had start up freezes and crashes galore, and couldn't figure out why. Did the clean install, and went back through everything I've added to my 400 DV since new, and updated the drivers for each device. Everything was working in harmony till I connected my Keyspan Dual Serial Adaptor and installed the drivers. My start up problems were back. There could very well be another problem causing it, but every time that adaptor is in line and the drivers for it installed, this 400 DV gets the bad jujus. I was using it with a StyleWriter. For now, the StyleWriter is back on the old Performa, and I'm using "sneaker net" to run a floppy downstairs to print there. At least till I can rustle up a USB printer.
As a side note, there's an article about modem setting issues associated with the Keyspan adaptor / software.
It's in the Apple Knowledge Base under Tech Info Library...dont have the link handy but it's TIL ID#25025. It seems the Keyspan software conflicts with the internal modem settings. I had that problem too, which hasn't reappeared since I disabled the adaptor and software. Again maybe it's something else in my system conflicting with it, but I have a hard time recommending something I've had trouble with and haven't found a work around for, as of yet.
just my 2 cents
regards
Doug