Raspberry Pi imager failure modes

I've been trying to write an image file to a microSD and it seems that
nothing happens. Even cancelling the write, nothing happens. The progress
bars just keep flying across the window. It's been well over an hour, from
a file in Downloads, so it can't be a network delay.

Presumably the microSD card is faulty, but I'd be more confident in that
if some explict error message came up. It's especially odd that cancelling
the write doesn't seem to do anything.

Anybody know what Imager failures are _supposed_ to look like?

Thanks for reading,

bob prohaska