QuickTime 7.6.6 for Leopard is recommended for all QuickTime 7 users and according to Apple brings about "general reliability improvements for iMovie." Additionally, the update addresses a long list of security vulnerabilities related to maliciously crafted audio or movie files that could allow attackers to cause crashes or run arbitrary code. The update is available via Software Update or the Apple Support Downloads page. (Free, 68.63 MB)
Use VirusBarrier X6 to Find Internet Traffic Paths
Need to find out who owns a domain name, or where your traffic is being routed? VirusBarrier X6 has a number of network monitoring tools, including a built-in Whois search tool, and a Traceroute feature. If you use the latter, you can even display a map after the traceroute has completed, showing exactly where in the world data passes between your Mac and a selected IP address.