UITableView background color does not change
You also need to set your UITableView's backgroundView property to nil on recent (since 3.2) versions of iOS.
As such, adding...
tbView.backgroundView = nil;
...should sort your problems.
That said, if you want to maintain compatibilty with pre-3.2 devices, you should check for the existence of this via the instancesRespondToSelector
method before calling it.
Make sure you have the following 3 options set:
tbView.opaque = NO;
tbView.backgroundColor = [UIColor clearColor];
tbView.backgroundView = nil;