Clicking on date not going to the latest post for some threads

Hi,

I am having an odd problem with my forum, http://www.commodoresplus.com.au - usually when you click on the time/date of the last post, it takes you to that post (so, for example, page 20.) However, on one particular thread (http://www.commodoresplus.com.au/forums/topic/t3-vr-lexcen-build/) it is not going to the right post, instead it is just going to the first page.

Any ideas?