Can't have multiple videos open at the same time?

I often start buffering another video when one is finished, so I usually tend to have 3-4 videos open at times. However, about a week ago, the adobe flash plugin would crash. So, I followed this guide: http://support.mozilla.com/en-US/kb/The+Adobe+Flash+plugin+has+crashed?style_mode=inproduct I also disabled the plugin container. Now, the plugin stops crashing, but firefox stops responding whenever I open a third video. Then, firefox itself crashes. Please help! == This happened == Every time Firefox opened == About a week ago.