This one still works.
I haven't upgraded to 3.7 just yet (should be within the next week or two), so in the meantime this helps my members. Thanks!
Oh, and for those that haven't read (or don't want to read) through these posts, you need to make sure that your settings are correct by going to...
ACP > vBulletin Options > General Settings > Thread/Forum Read Marking Type
....and make sure that the "Thread/Forum Read Marking Type" option is clicked on "Database (no automatic forum marking)"