Table loading hangs at 'Processing' in IE7

Hello,

I have a strange problem: my code works fine in FF and Chrome, but not in IE. (Well, not so strange after all...) In IE7 the table loading always hangs before displaying real data. I can only see the header and the footer, column names, and the 'Processing' message. Of course, no browser error message. I've tried debugging with the very little possibilities I have on IE7, but no luck.

So far I've checked:
- Every JSON response in validator
- JS in validator
- Used FireBug in FF, reported no error

I'm pretty stuck here, could you please help?

Cheers,
Adam

PS: http://debug.datatables.net/opuniy