Stuck in mirkwood arena no spiders to kill can't find radagast!!!

[oogie]

I went into the arena where radagasts house is in mirkwood.
I got killed by the spiders so consequently the game reloads.
When the game reloaded i was back in the arena again but there was no spiders to kill and nobody there exept me and my companions. I have tried the remedie to do with going into the game, quiting then going back in but it still hasn't worked.
what do i do ??? !!
love this game to bits really want to get it sorted
has anyone else had this problem?
open to any ideas

Please note I'm on single player on PS3

Thanks
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In the end i wasn't able to fix the actuall problem but it didn't matter. (this may prove useful) I went online instead and found someone who was near enough the same point as me, i then joined their game and problem solved. I was able to move on in the game even after the host had quit If you don't already know you can save the gme that you joined to online and save it as your own. note : when you join a game online you DO NOT lose any items, your level or anything else from your character.
What happened to me was the only bug/glitch i have ever experienced.