My primary disc works fine using my Xecuter 2.3 Lite and Avalaunch, but my friend, using (Xenium and Evox, I think) has the same problem as you. You might try switching dashboards, though I don't know if it is chip or dashboard related.
When I put in the bonus disc, however, it said something like 'updating Xbox live' (I had my Ethernet cable unplugged, fortunately), and I freaked so I turned it off really fast.
Anyone know what that is all about? I don't use Live, but I was worried it might try to over-write my dahsboard with a new M$ dash or something.
Anyone seen this type of behavior on this or other games? If so, what should I do?