If zero blocks are produced over several hours then that suggests there is a problem somewhere - I didn't know what the problem was, and wasn't about to risk things as a consequence of my ignorance. I waited 2 hours for the block to move and nothing happened. I simply played it safe out of my own ignorance. I didn;t expect it to be a major problem, but there was a small enough issue to make me react.
If the problem had persisted for a few more hours I suspect many other people would have made the same decision as me and bitcoin prices would have started to crash. Thankfully there was no major issue, and the price was about the same when I bought them back.
Allright, thanks for the explanation. Makes sense.