Not sure about that one, Paul. That's quite unusual. Did something activate on your PC during your round, perhaps windows update, a pre-set virus scan or something similar? It's also possible that the flash plugin began having some sort of problem, was about to crash and you suffered the results of that. The plugin may have attempted to recover on its own, but wasn't able to and then, as you say, the weird stuff started happening.
Were you able to submit a bug report by chance? If not, that's no big deal, but keep an eye on it and next time you see it happening (or if it becomes a regular occurance) throw us a bug report so we can try to see what's going on there.