Scream is there ever going to be an official fix to this from what I remember the problem is because when ever a user does an action you update a table w3t_online and insert the time in field O_Last. The problem is when you do this the time you insert isn't modified for a particular time zone. Therefore anyone who is using the site whose time zone is behind that of the site will be erased everytime someone looks at the pages as it will appear they have been ideal for more than 10 minutes, as when it does the comparision it uses the adjusted time. A site which has it's server time set at -12 GMT would not be effected, a site like yours set a US time zone would only be very slightly effected but European and Japanese sites, or even those on the east coast in the US would be more affected. I hope this makes some sense. All you need to do is not adjust the time to the users time zone when you do the comparison.
Dan