Description
When I try to view an existing thread while signed in, I get an "A required field called ip is missing or has an invalid value." error message.

This is from a new forum account; if there's a verification e-mail, I've yet to receive (or respond to) it.

I probably won't be able to view responses when signed in, so if there are steps I need to take or more info is required, please send a PM. I will also try to check this thread while signed out.

Steps to reproduce:
1. Sign in.
2. Search, or open a sub-forum from the main forum page.
3. Click a thread link.

Expected result:
The messages in the thread are displayed.

Actual result:
Get the error message:
vBulletin Message

A required field called ip is missing or has an invalid value.
System:
OS X 10.10.5
Firefox 54.0.1