Users dissappearing after upgrade to 3.9.3

After I upgraded from 3.9.1 to 3.9.3, users are randomly appearing offline, even though they're not actually signing out.

I first heard about this issue here

http://community.spiceworks.com/topic/493600-spark-users-disappearing-after-3-9- 2-update?page=1#entry-3328488

Anyone else have the same issue?