It might be that individual ISPs are blocking it.

Interesting note I just did a Google search “is grooveshark blocked in Canada” and this thread was on the first page of the Google hits.

BTW not blocked here in AZ

3M80 2M22 6QS8 2M2 1EP500 Sony BDP-S590 Panny-7000 Onkyo-3007 Carada-134 Xbox Buttkicker AS-EQ1