I've made a support ticket but thought I'd ask if anyone else has this problem.

After upgrading to 4.2 the unread content feature is not working for quite a few of my users. It's working for me in Chrome, but not in Opera, even though the Invision Site (ie, this forum here) does work. Strange.

Anyone else got the same problem?

Okay. It looks like the error was related to the amount of "content" that was considered "unread" by the forum.

Clicking the regular "unread content" button was not loading, but when I filtered it, for example by making it topics/forum posts only, or reducing it to 7/14 days, it then loaded fine.

I've advised people to use the "mark read" feature and then try again, and it's worked.

Perhaps the upgrade changed what was considered "unread" and that was too much stuff to handle?

There is actually a way to edit what the default for unread content is if you go into:

System -> Content Discovery -> Streams.

You can edit Unread Content and keep it as default.