If this happened with Google, people would be all over it. Basically, there are reports that MSN's cache view is having or had some past difficulties. Clicking on the cache link brings you (sometimes) to a page that reads:
Internal Server Error - Read
The server encountered an internal error or misconfiguration and was unable to complete your request.
This is reported to occur with sites that only have the url listed in the results. To me that means that MSN didn't index the page yet, and has nothing to show in the local MSN cache, as of yet. Give it some time, I am suspecting.
Forum thread at WebmasterWorld.