Sessions failing due to multiple CFID / CFTOKEN cookies

Richard or James, Was the cause of this issue ever determined for either of you? We're having the same issue with a small percentage of users.  We're detecting the double CFID entry in cgi.http_cookie and running a javascript to clear all our domain's cookies when we find the double CFID. We also set a tracking cookie so we don't try to clear that user's cookies again in case the double CFID doesn't go away. I believe that CF is setting a CFID and CFTOKEN for both www.domain.com and .domain.com and maybe that's why it's getting confused. However this is just dealing with the issue, not correcting it. Any info from your end would be appreciated. Thanks