Comment 7 for bug 247369

Same problem here. Something like this:

You open a page that contains a flash object, like YouTube, and then open another tab with other flashes. Then, if you close the second tab with the flash, the first instance of flashplugin disappear and a gray box stay in place. I'm using Lucid, and this bug is really annoying. Right now I've left my laptop on to load a Vimeo's video, and when I came back, closed a tab with YouTube, and the plugin disappeared. Now, I'll reload the entire clip.

Sometimes, if I put browser to "Work offline" and close/reopen tab, the movie is back there, from cache. But rarely works.

It's an old bug, I've seen this happen for a long time.