Use Google Chrome Built-In Flash In Firefox For (Probably) Less Crashes
I had some issues with Adobe Flash crashing very often using the latest Firefox 4 so I've searched for a way to fix this and found a topic on AskUbuntu which says to use Chrome's Flash plugin in Chromium so I though - why not do it for Firefox? - and it's actually working quite well for now.
Chrome uses a built-in Adobe Flash plugin which seems to work better then the regular Flash. But there's a catch: you must install Chrome (and keep it updated if you want further Flash updates) even if you don't use it.
Use the built-in Chrome Flash plugin in Firefox
1. Download and install Google Chrome (I for one prefer the unstable branch but I guess any version will do)
2. Open a terminal and copy / paste the following commands:
mkdir -p ~/.mozilla/plugins
ln -s /opt/google/chrome/libgcflashplayer.so ~/.mozilla/plugins/
3. Restart Firefox.
The exact same instructions above also work for Chromium (yes, using the ~/.mozilla/plugins/ folder even though it's for Chromium).
Note: I've tested this with the latest Firefox 4 32bit only (and Chromium 32bit)! It should work with older Firefox versions too though.