I am seeing this a lot with all different types of sites. This is the first thread I've seen on this.
I have tried executing this query using different HTTP proxys all on Google UK & US and have had the same mysterious results.
The results are from executing a cache: command and then only a 1 result SERP appearing with the traditional items such as Title and Meta Description. The listing also has the traditional Cached hyperlink:
this then throws up tradtional listings based on the URL but not using the cache.
Any other threads people know we can follow?