My main concern is this: If the manufacturer gets punished for failing to properly support out of warranty hardware, they'll just stop altogether. Too many manufacturers will already refuse to talk to you about out of warranty equipment.
Since they tried to help, I'd prefer not to see them punished for this mistake. Think of it like good samaritan laws: They protect a person who stops to offer aid to the injured, from being sued.
My other thought is that perhaps there was some hidden problem that something in the update triggered. Updates often have new functionality, or may write to memory not used before, so it isn't too hard to imagine them tickling an existing bug. For a car analogy, imagine you bought a used car from a friend and complained that it shook horribly at 75, but since your friend never went over 65 he never noticed when the tires and alignment deteriorated to that point.
Finally, I'm appalled that they don't make old firmware versions available. That would be the appropriate response to your problem. Hopefully you can find someone helpful who has the old firmware around, either inside or outside the companies. Definitely appropriate for people to be warned that these updates can cause problems.