Sorry, just came across this post. If you haven't found a solution yet, hopefully this will help.
I believe that performRequestWithHandler can be called on any thread, so UI changes should be dispatched to the main thread.
dispatch_async(dispatch_get_main_queue(), ^{
//update UI here
});
Or in the case of reloading table data you can use:
[self.tableView performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:NO];