Do any readers have this problem, or know someone who does? It reminds me a bit of prosopagnosia, or face blindness. I suspect both speech and face recognition utilize special modules in the brain, which could be subject to mild dysfunction.
A reader writes:
Saw your blog, I have that problem too - it usually happens to me when 1) tired, like at the end of an observing night or 2) at a party or dinner with lots of conversation around me.
The experience for me is that I hear the words clearly, but they don't connect to a symbol in my brain - someone will say, "would you like a roll" and I literally cannot place an image of what the sound "roll" is - this may happen more often than I realize for I know I have developed protocols to deal with the environment (like say no to all requests or limit the field of view)
From the comments: the condition is known as Auditory Processing Disorder (APD).