According to an Apple support discussion thread, a number of users are reporting errors when trying to stream music to an Airport Express or Apple TV following installation of iTunes 8.0. Users reporting unknown errors -15000 and -3256 have found some workarounds, however, ranging from changing firewall settings to turning on IPv6. Are you having problems with your Airport Express after installing iTunes 8.0? Let us know in the comments. [via Engadget]…