Hi there,
i also have the same problem with you after upgrade to v1.8 using Softaculous. After some troubleshooting, it seems to be due to the both default theme & template. Not sure have you notice, after upgrade my Disclaimer don't work as well.
It seems to be a temp fix, i have to setup another testing v1.8 and used this theme & template and it work fine. Now i fixing other issue too. Such as when we using mobile, there is some small display issue. Not sure can anyone confirm on it or have same issue (when reading post, the background color become purple)
Attach is the so call default, maybe you can give it a try. Not sure will it help
Think we may having the same "other v1.8 issue"
Update:
Maybe you can check this as well.. this is what was given. Maybe you can give it a try
i also will give it a test soon as well
http://community.mybb.com/thread-158870-...pid1100165
you can refer to my problem here
http://community.mybb.com/thread-158948.html