After much to and fro with Ubi Support, and much jumping through hoops, they tell me it's "been forwarded up to the development team for further review". Whether this is all circular I don't know, since it was En0 here who is listed as "Trials Developer" who advised me to contact them in the first place.

I'm now on a wired connection, using OpenDNS, with default MTU, and no different config on my end had obviously different results. The leaderboards server kicks me after about 20-40 mins in, regardless what my settings are or what track I'm playing.

Many people in these threads seem to have had the exact same issue in recent months. Let's see if the devs acknowledge and fix it.

http://forums.ubi.com/showthread.php...o-leaderboards
http://forums.ubi.com/showthread.php...e-racing-ghost
http://forums.ubi.com/showthread.php...bisoft-servers
http://forums.ubi.com/showthread.php...he-leaderboard
http://forums.ubi.com/showthread.php...ing-this-issue
http://forums.ubi.com/showthread.php...e-bug-17-01-15