If you use the cffeed tag and get the following error. It's a known bug in CF 8 and 9.
java.lang.NoClassDefFoundError: Could not initialize class coldfusion.syndication.FeedDateParser
Apparently this hasn't been fixed yet by Adobe, so in order for this to work you need to modify your sandbox/resource security settings to allow read/execute access to..
For CF Ent..
For CF Std
The link to the bug report is http://www.elliottsprehn.com/cfbugs/bugs/75118