Hi Donna!
I know this is really a longshot, but i found this: http://www.zdnet.com/blog/apple/icloud-bug-creates-thousands-of-duplicate-bookmarks/12084. Given that the IP is supposed to be registered to Apple, and that it does not appear to have a host. Could it perhaps be that this is an iCloud server that has a ton of links/bookmarks to your site? I know it's a stretch but still...
If you click on the entry in GWT, are you able to see what subpages are linking your way? And are the links to your site direct links, or do they show as "via intermediate links"? If so, then it could be that someone has scraped your site. Or could it be that your client (or you clients hosting provider) has some sort of backup server or test/staging environment that resides on this IP and that for some reason was available to GoogleBot? See http://webmasters.stackexchange.com/questions/54100/gwmt-show-non-existent-backlinks-via-intermediate-link.
This is just me guessing, to please don't take this as definitive answers/solutions... 
I hope you'll figure it out. Please share if you find the answer to this.