This was reported by Kidman here:
http://kmeleonbrowser.org/forum/read.php?f=2&i=3517&t=3517
"Some other small thing:
...
- about:cache-entry doesn't work"
This has been marked "Closed" on our Beta bugs page based on this from myself:
Resolution: (11/30/2004) This doesn't appear to be a bug. This does work when viewing actual cache entries following the links from the about:cache page. There doesn't look like there is an easy way to remove it from the about:about page so we'll just have to educate users about this.