A WebmasterWorld thread reports that someone is noticing that his site's Sitelinks in Google are pointing to a different site. I am not sure how that is possible. How can Google link a Sitelink for one site to a different site? But according to this webmaster, it is true.
I do not have any proof that this is happening, nor will I ever get proof because WebmasterWorld does not allow examples. But I believe it is possible that with DNS changes and shared IPs, it is possible that Google can be confused and link to the wrong place.
If this happens to you, the first thing you should do is block those Sitelinks in Google Webmaster Tools. Then post evidence at Google Webmaster Help.
As Tedster said at WebmasterWorld:
Sounds like a particularly nasty data bug. Does that sitelink show up in your Webmaster Tools account? If so, you can veto it. If not, you could take the issue up on the Google Webmaster forum or try a reconsideration request.
Forum discussion at WebmasterWorld.