Hey I can answer that.

The Nuke theme directory layout changed a little in Nuke6.5
The forum template files moved from
modules/Forums/templates/Yourtheme
to
themes/Yourtheme/forums

Now the deal on the mods are that they will have to be modified, and all paths in the *.tpl files will need to be changed to reflect the new paths to the template files, which now reside in the
themes/Your Theme/forums folder

so, for instance, where you have
modules/Forums/templates/Yourtheme/images/cellpic1.gif

you now have
themes/Yourtheme/forums/images/cellpic1.gif

mikem