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I've seen the same thing on some of my sites... This guy provides a pretty good analysis http://socialmediatoday.com/georgestevens48/1317336/google-rewriting-page-titles-time-brand It sounds like it's not so much about colons, but more about moving brands to the front of the title.  Only time will tell whether it's a test or a permanent change. I also want to add that I've seen this for general searches that do not include my company name / brand.