We are discussing a similar issue here:
http://social.technet.microsoft.com/Forums/en-US/Profile/thread/ccfd8cde-ab9f-4296-ba18-3bd6e73c4a73
I have seen where it takes a few days for the activity to show up in the profile. I think a batch process runs periodically (my guess). However, in the article I linked we suspect there might be windows of time where the system is blind to activity.
Richard Mueller - MVP Directory Services