That could be the problem. It may be that the plugin has outgrown the old OS. I'm having problems with shockwave + chrome + Vista and XP. Might be an idea to do a search about the issues. They could be quite common now.
This morning, my Avast software gave me updates to Firefox (40.0.3), Shockwave plugin and Java Runtime Environment 8. I was hoping these would solve my freezing problems. After getting the updates, my pc froze within several seconds. So now it appears my only alternative is switching to Chrome.
Is it possible that Chrome would not carry over the freeze problem, Shockwave/Script problems I've had on Firefox?
For what it's worth, I completely deactivated shockwave and java in Chrome and the problems have disappeared. Chrome does not support shockwave properly nor java it seems. Pain in the neck because I now can't use some websites' embedded music players. But it's better than having the whole thing crash after a few minutes.
