Comment 13 for bug 451125

I've investigated and it looks like the model pre-fetching mechanism is to blame. Pre-fetching a model invalidates the URL (it's a one-shot URL), despite the "clever" mechanism meant to avoid this. Disabling the mechanism seems to fix the issue here.
I still need to understand why this mechanism was here in the first place, though. It looks to me like it was introduced to work around a bug on grooveshark's side where invalid URLs were returned, which was fixed since then.