I am sorry if this is elsewhere but I haven't found it yet.
ISSUE: I just upgraded to RH8 from RH6 and the related topic popups that were converted over (from RH6 top RH8) as well as all graphic popups are not working. The only links I can get to generate are links to another topic within my project. All of these links and popups where working the last time the project was generated in RH6.
Perhaps try clicking Tools > Update DHTML Effects in Topics?
I did the DHTML update and that seems to have solved the problem as far as the Related Topic Popups working but before when you would click on the popup link it would open the related topics box directly above the link now that box is at the top of the page (related topic link is typically at the bottom).
Also the DHTML update did not help in regards to graphics opening up from links - As I said this all worked before.
Appreciate your help thus far.