Youtube (Browsed on safari) not works in the background on multi tasking

I often use my ipad for long periods of time on study and need something (music) running in the background and i want to specify to youtube because i dont want to use all the GB's on the ipad on downloaded music.

I had no problem at first but after i updated my ipad to ios 6.1 and when i double click the homescreen button then slide to the right i click the play button which apears near a safari icon but IT DOES NOT RESPOND AND I KEEP PRESSING AND STILL NO REUSLT please help. Any solutions please