OP: Usually when you attempt to open a PPC application in Snow Leopard and it indicates that you need to install Rosetta, it will then do a download and install over the internet. You also have the option to install manually from the Snow Leopard Install DVD.
Is your Mac connected to the Internet? Any firewalls, or other blocks? You are at 10.6.8, can you continue to run Software Update, and download updates, for example the latest version of JAVA to avoid the current malware problem?
Recently I have been experimenting with various Snow Leopard installs into Parallels 7 for use of Rosetta in Lion. One of the times, I purposely did not check the install Rosetta in the Options before install. When I attempted to run a PPC application, indeed, Rosetta downloaded from the Internet and installed and the app run fine.
If you have MobilMe, you can log in and Apple is giving away the Snow Leopard Install DVD for free. I received mine about 4 business days after I ordered it on MobileMe.