problem after update new version

[frupunch]

good day to all,

i got a problem after updating the forum from 3.6.4 to 3.6.8

the last poster's name became the the thread starter. which means when we enter a sub-forum, we can see many threads, and under the thread title, there are the name of the thread starter. but after my update, the problem is the name suposed to be thread starter under the thread titile became the last poster's name...

what's the problem there? what should i do?

hope you can help me.
thank in advance.