I had a problem ever since I moved to Firefox 3.6 where if I installed the java plugin Firefox would just hang. I didn't matter if I installed the sun or the iced tea one, or whether I installed via yast or manually using the files from Sun.
Been searching for ages and have found plenty of forums with people who have this problem but no solution.
I think I've finally found a workaround.
Install the configuration mania extension for firefox
https://addons.mozilla.org/en-GB/firefox/addon/4420/
and open it up from the tools menu. Go to the add ons tab and check the bottom option "run browser plugins in a separate processing thread from the main firefox process".
This is probably somewhere in about:config but I wouldn't know where.
Close firefox, install the sun java and plugin from yast (remove the iced tea if it's installed), start firefox and the hanging problem should now be fixed.
I hope this is of use to someone else.