Here's my problem and what i did to fix it.
Q (problem):since at school, students are NOT administrators, it wouldnt let me download the plugin from jagex. (the little popup window that you click accept on, or you can click "always trust content from jagex ltd." and so yeah, it wouldnt let me download that soz therefore i couldnt play.
A(my solution): k now heres what i did to play RS at school... Download eliteswitch onto a flash drive at the public library or at home, then install it at school, load up your favorite world and for some reason when i clicked the..."always trust content from jagex ltd." thingy, it actually worked, this may not be the solution for u but it worked for me...