Trying to debug the networking code for an embedded widget. It's being incredibly frustrating (large amounts of Other People's Code, not well documented, and not behaving itself; the poor documentation of certain aspects of the MCU doesn't help either).
There's some issue that has to be a corrupted list. Could, just conceivably, happen as a result of network activity.
Just to narrow things down, I disconnect the Ethernet cable from the board.
And, at that very moment, the overhead light dims abruptly as one of the two bulbs burns out.