Problem with " View posts since last visit "

my forum here

I have had a number of my users report the same fault, that when they click on " View posts since last visit " there appears to be no new posts, when there quite clearly has been.

I am using phpBB3 which I understand now may be causing the problem and therefore may not be able remedy - could someone confirm that?

If I shift to one of the other versions will it be possible to deal with the the View posts issue?

I'm losing Users over this problem and could do with a quick fix if at all possible

Ta