Try using Firefox 3.6 that works with RealPlayer. You could [http://portableapps.com/apps/internet/firefox_portable/localization#legacy36 download] and install the portable 3.6 version whilst keeping the Release firefox 5 for day to day work, with all your bookmarks and settings. You could also consider the [https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ compatibility reporter] There are many [https://support.mozilla.com/en-US/search?w=2&a=1&created=0&created_date=&updated=0&updated_date=&sortby=0&asked_by=&answered_by=&num_voted=0&num_votes=&q_tags=&q=Real+Player++5 thread] [https://support.mozilla.com/en-US/search?q=RealPlayer++5&num_voted=0&num_votes=&asked_by=&answered_by=&q_tags=&created=0&created_date=&updated=0&updated_date=&sortby=0&a=1&w=2 s] and some seem to offer conflicting answers, but it is working with Firefox 3.6. I do not currently use Real Player myself.

I had to go back to Firefox 4. The strange thing is on another computer works fine using Firefox 5, even saying that the pluggin is incompatible

Maybe the other computer has disabled compatibility checking via Compatibility Reporter, (or some other method) or maybe Real Player have now updated their Addons. Note Firefox 4 is no longer supported, and is considered NOT to be secure, that is the reason I suggested firefox 3.6, which is currently still supported and secure.

GOOD NEWS! Real Player has been updated and is now compatible with Firefox 5