Ok so this is weird.
I thought my mac's keyboard had developed a broken key, but after some testing it's only broken when interacting with some other keys.
The left shift key doesn't work with a handful of other keys, see the following output with the shift key depressed:
qwertyuopASDFGHJKLZXCVBNM
Also note the lack of an i
in that output. That key works, but when the shift key is depressed it doesn't output anything.
It doesn't appear to be a software issue, as it's exactly the same on both my imac and when hooked up to my macbook.
Ghost in the machine?
Best Answer
Given the problem appears on two Macs, this suggests a hardware fault. If the keyboard is not too old, take it to an Apple Store. They may be able to replace it for you.
The strange behaviour you are seeing could be because a circuit is damaged and causing ghosting. Microsoft's article on ghosting explains more: