Thanks Devinder.  I think you're on the right track, in that there MUST be some kind of page reload happening before the full tracking runs.  However all other tracking works perfectly, it is only referrals from search.yahoo.com that are affected in this way.  I've tested by clicking through from Ya...

We have an ancient VISTA rule which populates our Tracking Code report.  It records plenty of referrals from Yahoo which appear as 'search.yahoo.com' in the Tracking Code report.  However these do NOT appear in the Referring Domains report or other referrer reports.  For example, in August the Track...