Thanks for getting back at me, zzj. Unfortunately, adding those files didn't resolve the issue - my browser alternates between "waiting for pandora.com" and "waiting for audio-sjl-t1-2.pandora.com" and the message Pandora spits out is that it's "taking longer than expected..." the 't1' varies to 'a' sometimes, and I can see this reflected Fiddler.
Any other ideas? This was working perfectly before I mistakenly updated the portable Firefox version. It randomly started playing music last night but doesn't work again today.