Out of nowhere, 8 keys on my keyboard failed all at the same time. They are the y, u, i, o, numlock, /, * and - keys (the last four are over the numeric keypad).
I’ve popped off a couple of the key caps and there’s nothing blocking them; I tried pressing down the membrane without the keycap, and no change.
Is this keyboard dead dead dead? Any magic resuscitation techniques?
Roddy
eta: this happened in the middle of the day after using the keyboard for nearly 3 hours today. Needless to say, perhaps, but I am now using a different keyboard.
What did you spill on it?
The reason those keys all failed at once is most likely because the printed circuit board under the keys got damaged, in the area where the circuitry for all of those specific keys run together. As for how that section of the board became damaged…what did you spill on it? 
Absent any additional information, the most likely cause for such a failure is of course a liquid spill, in which case thoroughly drying the keyboard *may *resolve the problem. If that wasn’t the cause (which seems to be the case if the keys ‘spontaneously’ failed), then your guess is as good as mine, but most likely it’s a write-off. Luckily, keyboards are relatively inexpensive.
Doesn’t have to be a spill. Pretty much all keyboards have a switch matrix. Meaning, there are about 20 traces on the circuit board and they’re mixed up so that you can press 2 (or 3 or 4 or more, depending on the position and hardware expense) keys at the same time and the controller in the keyboard can figure out which keys are pressed without having dedicated connections and reading hardware for each key switch.
This reduces the complexity of the circuit board and cost of the controller hardware, but it also generally means that if one of the traces on the board breaks, you lose a whole set of keys. So, if you didn’t spill anything, it’s likely the circuit board has a broken connection somewhere. Probably easy enough to fix with some solder, if you can find the broken trace/wire connection.
Keys on a keyboard are organized into rows and columns (the switch matrix that Superfluous Parentheses was describing). Typically you’ll lose keys like M, J, K, and I in a diamond-like pattern, but depending on the layout of your particular keyboard a failure like the OP is certainly possible.
The bad news is that this probably means you have lost an entire part of a circuit. With a coffee spill you can usually wash out the keyboard and it will be fine. This type of failure is usually not recoverable.
If you are handy, you can try opening up the keyboard. With a little luck there will be a ribbon connector that connects the keyboard membrane to the microcontroller. If you pull this ribbon out and put it back in the keyboard may function normally, if the problem is a bad electrical connection at that location, due to dirt or just a slightly damaged contact.
Most likely though, the keyboard is futzed. As was mentioned, if you are handy with a soldering iron you may be able to fix it. Otherwise, toss it.