Do you see individual subject "activations" that make sense? In a lot of subjects? In overlapping places?
If the answers are "yes, yes, yes", (or even "maybe, maybe, maybe") then a little more blur -- 6 or 8 mm -- might help. An additional possibility is to re-run the individual subject analyses with the addition of AnatICOR de-noising and nonlinear anatomical registration. The latter will line up the subjects' anatomies somewhat better, and can bring out group activations that are otherwise not found -- since they wouldn't have lined up.
