It was only one user who got it, Steffen Duus. He got it on EasyDiscuss, I am not sure if it was then visiting the frontpage or trying to enter a thread.
I was able to "fix" it by disabling: EasyDiscuss Admin > Settings > General > Tabs > Show Custom Fields
After that he still kept reporting weird bugs in EasyDiscuss such as not being able to see his own role badge under his name and stuff. But for the most part it seems to be "fixed"... still think there is something wrong with the database for his account.